Nonaqueous electrolytic solution and nonaqueous electrolytic solution secondary battery

ABSTRACT

An object of the present invention is to provide a nonaqueous electrolytic solution and a nonaqueous electrolytic solution secondary battery capable of showing high output characteristics at a low temperature even after the battery is used to some extent, and capable of showing good high-rate properties, and further capable of improving safety of batteries. The nonaqueous electrolytic solution includes a nonaqueous solvent, an electrolyte dissolved in the nonaqueous solvent, (I) a difluoro ionic complex (1) represented by the general formula (1), and (II) at least one compound selected from the group consisting of a specific cyclic phosphazene compound, siloxane compound, aromatic compound, cyclohexene compound, phosphoric acid ester compound, fluorinated linear ether compound, fluorinated cyclic ether compound, and boric acid ester compound, and 95 mol % or more of the difluoro ionic complex (1) is a difluoro ionic complex (1-Cis) in a cis configuration represented by the general formula (1-Cis).

TECHNICAL FIELD

The present invention relates to a nonaqueous electrolytic solutionhaving excellent output characteristics at low temperature, and abattery such as a lithium secondary battery using the nonaqueouselectrolytic solution. Further, the present invention relates to anadditive useful for the nonaqueous electrolytic solution.

BACKGROUND ART

In recent years, there have been rapidly increasing demands for not onlyelectricity storage systems for small-sized and high energy densityapplications, for example, information-related apparatus, communicationapparatus, i.e., personal computers, video cameras, digital cameras,portable telephones, and smartphones; but also batteries with largecapacity, high output and high energy density which can be used forelectric vehicles, hybrid vehicles, and auxiliary power systems offuel-cell vehicles. Moreover, there have been increasing demands forbatteries which can be used for a long time even in electricity storagesystems for large-sized and high power applications, for example,electric power storages. As one of the candidates for such electricitystorage systems, nonaqueous electrolytic solution batteries have beenunder active development, such as lithium ion batteries, lithiumbatteries, and lithium ion capacitors.

Lithium secondary batteries mainly include a positive electrode, anonaqueous electrolytic solution, and a negative electrode. As negativeelectrodes for lithium secondary batteries, known are, for example,metal lithium, metal compounds (for example, elemental metals, oxides,alloys with lithium, and the like) capable of occluding and releasinglithium, carbon materials, and the like. In particular, lithiumsecondary batteries where carbon materials capable of occluding andreleasing lithium such as corks, artificial graphite, natural graphite,and the like are used have been put into wide practical use. Forexample, it is reported that in a lithium secondary battery where ahighly crystallized carbon material such as natural graphite andartificial graphite is used as a negative electrode material, anonaqueous solvent in a nonaqueous electrolytic solution may bereductively decomposed on the surface of a negative electrode uponcharging, resulting in generation of decomposition products or gases.This may interfere with the desired electrochemical reactions of thebattery, which in turn, may decrease cycle characteristics.

Further, in a lithium secondary battery where metal lithium or an alloythereof, an elemental metal such as silicon and tin, or an oxide is usedas a negative electrode material, pulverization of the negativeelectrode material is promoted during cycles although it has a highinitial capacity. Therefore, a nonaqueous solvent is more susceptible toreductive decomposition as compared with a negative electrode made of acarbon material. As a result, the charge/discharge efficiency at thefirst cycle is known to be decreased due to an increased initialirreversible capacity of the battery. It is also known that this maysignificantly decrease battery performances such as battery capacity andcycle characteristics. A negative electrode may react with lithiumcations or a solvent of an electrolytic solution when lithium cationsare intercalated into the negative electrode upon charging at the firstcycle. This may form a film containing lithium oxide, lithium carbonate,and lithium alkylcarbonate as the main components on the surface of thenegative electrode. This film on the surface of the electrode which iscalled a Solid Electrolyte Interface (SEI) may, in nature, havesignificant impacts on battery performance. For example, it may reducereductive decomposition of a solvent to prevent deterioration of batteryperformance. As described above, one of the disadvantages is thatlithium may not be smoothly occluded into and released from a negativeelectrode due to adverse effects such as accumulation of decompositionproducts and generation of gases from a nonaqueous solvent, andpulverization of a negative electrode material, resulting in significantdeterioration of battery characteristics such as cycle characteristics.

Meanwhile, as a positive electrode, known are, for example, LiCoO₂,LiMn₂O₄, LiNiO₂, LiFePO₄, and the like. It is reported that in lithiumsecondary batteries where these materials are used, a nonaqueous solventin a nonaqueous electrolytic solution may partly undergo local oxidativedecomposition at the interface between a positive electrode material andthe nonaqueous electrolytic solution when the temperature is increasedduring charging. This results in generation of decomposition productsand gases. As a result, the desired electrochemical reaction of thebattery may be interfered with, which in turn, may decrease batteryperformances such as cycle characteristics. As in the negativeelectrode, a film may also be formed on the surface of the positiveelectrode due to oxidatively decomposed products. This film is alsoknown to play an important role. For example, oxidative decomposition ofa solvent may be prevented, and the battery gas yield may be reduced.

As described above, conventional lithium secondary batteries have aproblem in that decomposition products and gases generated when anonaqueous electrolytic solution decomposes on a positive electrode anda negative electrode may interfere with the movement of lithium ions,and may cause the expansion of a battery. These may be responsible fordecreased battery performance.

In order to overcome the above problems and further improve batteryperformance such as long term durability and output characteristics, itis important to form an SEI having a high ion conductivity, a lowelectron conductivity, and a long-term stability. To this end, attemptshave been widely made for intentionally forming a good SEI by adding asmall amount (usually 0.01 mass % or more and 10 mass % or less) of acompound called an additive to an electrolytic solution.

For example, in a secondary battery where a graphite-based negativeelectrode with a high degree of crystallinity is used, a nonaqueouselectrolytic solution containing, for example, vinylene carbonate,vinylethylene carbonate, and/or the like has been used to minimizedecomposition of the nonaqueous electrolytic solution to obtain a highcapacity. Further, attempts have been made for improving storageproperties and cycle characteristics at high temperature (PatentDocuments 1 and 2). However, these are still less than satisfactory. Forexample, use of a nonaqueous electrolytic solution including ethylenecarbonate as the main solvent and containing 0.01 to 10.0 mass % ofvinylene carbonate relative to ethylene carbonate can not sufficientlyprevent an increased internal resistance of a battery when stored athigh temperature.

A nonaqueous electrolytic solution is disclosed containing aphosphorus-boron complex and the like as an additive for forming aneffective SEI, such as a lithium difluoro(oxalato)borate (PatentDocument 3). Patent Document 4 discloses an electrolytic solution whichcan improve a low-temperature property (the ratio of dischargecapacities of −20° C./25° C.) at 0° C. or below as well as cyclecharacteristics and high-temperature storage properties, theelectrolytic solution including both a difluoro(bisoxalato)phosphatesalt and a tetrafluoro(oxalato)phosphate salt.

Further, Patent Document 5 discloses a method of manufacturing lithiumtris(oxalato)phosphate.

It is noted that Patent Document 6 discloses a method of manufacturing aphosphorus-boron complex such as lithium difluorooxalatoborate used asan electrolyte for electrochemical devices.

Nonpatent Document 1 discloses a method of manufacturing a fluorocomplex having silicon or the like in the complex center.

-   Patent Document 1: Japanese Unexamined Patent Application,    Publication No. H08-045545-   Patent Document 2: Japanese Unexamined Patent Application,    Publication No. 2001-006729-   Patent Document 3: Japanese Unexamined Patent Application,    Publication No. 2002-110235-   Patent Document 4: Japanese Unexamined Patent Application,    Publication No. 2011-22193-   Patent Document 5: Japanese Unexamined Patent Application    (Translation of PCT Application), Publication No. 2003-505464    (Japanese Patent No. 4695802)-   Patent Document 6: Japanese Unexamined Patent Application,    Publication No. 2003-137890-   Non-Patent Document 1: J. Chem. Soc. (A), 1970, 15, 2569-2574

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Nonetheless, further improvements have been desired because theaforementioned nonaqueous electrolytic solutions cannot be said to havesufficient high-temperature storage properties or do not satisfy recentdemands for high-performance batteries. That is, although not a smallnumber of practical nonaqueous electrolytic solution batteries, whichare typically lithium ion batteries, are already available, anelectrolytic solution having sufficient properties has not yet beenobtained for applications where batteries may potentially be used undermore harsh environments, including in-vehicle ones.

Specifically, high output characteristics at a low temperature arestrongly desired to allow a nonaqueous electrolytic solution battery tooperate at a high output without aid of thermal insulation and heatingeven in cold climate areas. In order to achieve this, variouselectrolytic solutions have been proposed to date. However, the majorityof them remain unsatisfactory in that the output characteristics aresignificantly decreased after batteries are used to some extent(charge-discharge cycles have been performed for certain times; orstorage history at a high temperature is long) although the initialoutput characteristics are improved. Therefore, an electrolytic solutionis strongly desired which shows high output characteristics at lowtemperature even after a certain number of charge-discharge cycles orafter stored at high temperature. Moreover, it is required to improvesafety of lithium ion batteries through improving flame retardancy,preventing occurrence of expansion during charge and discharge, andpreventing overcharging that causes ignition and smoke generation. Thatis, an object of the present invention is to provide a nonaqueouselectrolytic solution and a nonaqueous electrolytic solution batterycapable of showing high output characteristics at a low temperature evenafter the battery is used to some extent, and capable of showing goodhigh-rate properties under ordinary temperature, and further capable ofimproving safety of batteries.

Means for Solving the Problems

The present inventors conducted extensive studies in order to solve theabove problem. Consequently, after comparing effects of separateaddition of the cis- and trans-isomer difluoro ionic complexes, thepresent inventors found that a cis isomer shows a higher effect forimproving output characteristics at low temperature after cycledurability tests. Further, by producing an electrolytic solution fornonaqueous electrolytic solution batteries including both theaforementioned six-coordinate ionic complex in the cis configuration anda specific compound shown in group II, the present invention provides anonaqueous electrolytic solution and a nonaqueous electrolytic solutionbattery capable of exerting effects such as flame retardancy, preventionof expansion during charge and discharge, or prevention of overcharging,depending on the combinedly used compound shown in group II.

That is, the present invention provides a nonaqueous electrolyticsolution for nonaqueous electrolytic solution batteries, the nonaqueouselectrolytic solution including a nonaqueous solvent, an electrolytedissolved in the nonaqueous solvent, (I) a difluoro ionic complex (1)represented by the general formula (1), and (II) at least one compoundselected from the group consisting of a cyclic phosphazene compoundrepresented by the general formula (II-1) below, a siloxane compoundrepresented by the general formula (II-2) below, an aromatic compoundrepresented by the general formula (II-3) below, a cyclohexene compoundrepresented by the general formula (II-4) below, a phosphoric acid estercompound represented by the general formula (II-5) below, a fluorinatedlinear ether compound represented by the general formula (II-6) below, afluorinated cyclic ether compound represented by the general formula(II-7) below, and a boric acid ester compound represented by the generalformula (II-8) below, wherein 95 mol % or more of the difluoro ioniccomplex (1) is a difluoro ionic complex (1-Cis) in a cis configurationrepresented by the general formula (1-Cis).

wherein in (1-Cis),

In the general formula (1) and the general formula (1-Cis),

A⁺ is any one selected from the group consisting of a metal ion, aproton, and an onium ion, and M is any one selected from the groupconsisting of Si, P, As, and Sb.

F is a fluorine atom, and O is an oxygen atom.

t is 2 when M is Si, and t is 1 when M is P, As, or Sb.

X is an oxygen atom or —N(R¹)—. N is a nitrogen atom, and R¹ is ahydrocarbon group having 1 to 10 carbon atoms and optionally having ahetero atom and/or a halogen atom (the hydrocarbon group optionallyhaving a branched-chain or ring structure when the number of carbonatoms is 3 or more).

When X is —N(R¹)—, and p is 0, X and W are bonded directly andoptionally form a structure as shown in at least one selected from thegeneral formulas (1-Cis-1) to (1-Cis-3) below. In the case of thegeneral formula (1-Cis-2) below where the direct bond is a double bond,R² is not present.

Y is a carbon atom or a sulfur atom. q is 1 when Y is a carbon atom. qis 1 or 2 when Y is a sulfur atom.

W represents a hydrocarbon group having 1 to 10 carbon atoms andoptionally having a hetero atom and/or a halogen atom (the hydrocarbongroup optionally having a branched-chain or ring structure when thenumber of carbon atoms is 3 or more), or —N(R²)—. Here, R² represents ahydrogen atom, an alkaline metal, or a hydrocarbon group having 1 to 10carbon atoms and optionally having a hetero atom and/or a halogen atom.When the number of carbon atoms is 3 or more, R² may have abranched-chain or ring structure.

p is 0 or 1, and q is an integer of 0 to 2, and r is an integer of 0 to2. Further, p+r≥1.

[In the general formula (II-1), R¹ to R⁶ are each independently asubstituent selected from the group consisting of a halogen atom, anamino group, an alkyl group having 1 to 10 carbon atoms, an alkoxy grouphaving 1 to 10 carbon atoms, and an aryloxy group having 6 to 12 carbonatoms; n¹ is an integer of 1 to 10; and the alkyl group, the alkoxygroup, and the aryloxy group optionally have a hetero atom and/or ahalogen atom;

in the general formula (II-2), R⁷ to R¹² are each independently asubstituent selected from the group consisting of an alkyl group having1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, analkenyl group having 2 to 10 carbon atoms, an alkenyloxy group having 2to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, analkynyloxy group having 2 to 10 carbon atoms, an aryl group having 6 to12 carbon atoms, and an aryloxy group having 6 to 12 carbon atoms, saidgroups optionally having a hetero atom and/or a halogen atom; n² is aninteger of 1 to 10; when n² is 2 or more, R¹¹'s and R¹²'s independentlyare optionally the same as or different from one another; a grouprepresented by OR⁷ and a group represented by OR⁸ are optionally bondedto each other to form a siloxane bond; and the siloxane compoundrepresented by the general formula (II-2) includes a siloxane compoundrepresented by the general formula (II-2′); and in the general formula(II-2′), R¹³ and R¹⁴ are each independently a substituent selected fromthe group consisting of an alkyl group having 1 to 10 carbon atoms, analkoxy group having 1 to 10 carbon atoms, an alkenyl group having 2 to10 carbon atoms, an alkenyloxy group having 2 to 10 carbon atoms, analkynyl group having 2 to 10 carbon atoms, an alkynyloxy group having 2to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, and anaryloxy group having 6 to 12 carbon atoms, said groups optionally havinga hetero atom and/or a halogen atom; n³ is an integer of 2 to 10; R¹³'sand R¹⁴'s independently are optionally the same as or different from oneanother.]

[In the general formula (II-3), R¹⁵ to R²⁰ are each independently asubstituent selected from the group consisting of a hydrogen atom, ahalogen atom, and a hydrocarbon group having 1 to 12 carbon atoms; andat least two of R¹⁵ to R²⁰ are optionally bonded to one another to forma ring; and

in the general formula (II-4), R²¹ to R²⁴ are each independently asubstituent selected from the group consisting of a hydrogen atom, ahalogen atom, and a hydrocarbon group having 1 to 12 carbon atoms; andat least two of R²¹ to R²⁴ are optionally bonded to one another to forma ring.]

[In the general formula (II-5), R²⁵ to R²⁷ are each independently asubstituent selected from the group consisting of an alkyl group having1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, analkenyl group having 2 to 10 carbon atoms, a cyano group, an aminogroup, a nitro group, an alkoxy group having 1 to 10 carbon atoms, and acycloalkyl group having 3 to 10 carbon atoms, said groups optionallyhaving a hetero atom and/or a halogen atom; and any two or all of R²⁵,R²⁶, and R²⁷ are optionally bonded to one another to form a ringstructure;

in the general formula (II-6), R²⁸ and R²⁹ are each independently asubstituent selected from the group consisting of an alkyl group having1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, afluorinated alkyl group having 1 to 10 carbon atoms, a fluorinatedcycloalkyl group having 3 to 10 carbon atoms, an alkyl group having 1 to10 carbon atoms and having an ethereal oxygen atom between the carbonatoms, and a fluorinated alkyl group having 1 to 10 carbon atoms andhaving an ethereal oxygen atom between the carbon atoms; and at leastone of R²⁸ and R²⁹ contains a fluorine atom;

in the general formula (II-7), R³² is a substituent selected from thegroup consisting of an alkylene group having 1 to 5 carbon atoms, afluorinated alkylene group having 1 to 5 carbon atoms, an alkylene grouphaving 1 to 5 carbon atoms and having an ethereal oxygen atom betweenthe carbon atoms, and a fluorinated alkylene group having 1 to 5 carbonatoms and having an ethereal oxygen atom between the carbon atoms; R³⁰and R³¹ are each independently a substituent selected from the groupconsisting of an alkyl group having 1 to 10 carbon atoms, a cycloalkylgroup having 3 to 10 carbon atoms, a fluorinated alkyl group having 1 to10 carbon atoms, a fluorinated cycloalkyl group having 3 to 10 carbonatoms, an alkyl group having 1 to 10 carbon atoms and having an etherealoxygen atom between the carbon atoms, and a fluorinated alkyl grouphaving 1 to 10 carbon atoms and having an ethereal oxygen atom betweenthe carbon atoms; and at least one of R³⁰ and R³¹ contains a fluorineatom; and

in the general formula (II-8), R³³ to R³⁵ are each independently afluorinated alkyl group having 1 to 10 carbon atoms.]

Further, the present invention provides a nonaqueous electrolyticsolution battery including the aforementioned nonaqueous electrolyticsolution, a positive electrode, a negative electrode, and a separator.

Effects of the Invention

The present invention can provide a nonaqueous electrolytic solution anda nonaqueous electrolytic solution battery capable of showing highoutput characteristics at a low temperature even after the battery isused to some extent, and capable of showing good high-rate propertiesunder ordinary temperature, and further capable of showing performancesuch as flame retardancy, prevention of expansion during charge anddischarge, or prevention of overcharging, depending on the combinedlyused compound, and capable of improving safety of batteries.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an analysis result from the single crystal X-ray structuralanalysis of (1a-Cis) according to Synthesis Example 1.

PREFERRED MODE FOR CARRYING OUT THE INVENTION

<1. Nonaqueous Electrolytic Solution>

The nonaqueous electrolytic solution according to the present inventionincludes a nonaqueous solvent, an electrolyte dissolved in thenonaqueous solvent, (I) a difluoro ionic complex (1) represented by thegeneral formula (1), and (II) at least one compound selected from thegroup consisting of a cyclic phosphazene compound represented by thegeneral formula (II-1) below, a siloxane compound represented by thegeneral formula (II-2) below, an aromatic compound represented by thegeneral formula (II-3) below, a cyclohexene compound represented by thegeneral formula (II-4) below, a phosphoric acid ester compoundrepresented by the general formula (II-5) below, a fluorinated linearether compound represented by the general formula (II-6) below, afluorinated cyclic ether compound represented by the general formula(II-7) below, and a boric acid ester compound represented by the generalformula (II-8) below, wherein 95 mol % or more of the difluoro ioniccomplex (1) is a difluoro ionic complex (1-Cis) in a cis configurationrepresented by the general formula (1-Cis).

-   -   wherein in (1-Cis) and (1-Trans),

In the general formula (1) and the general formulas (1-Cis) and(1-Trans), A⁺ is any one selected from the group consisting of a metalion, a proton, and an onium ion, and M is any one selected from thegroup consisting of Si, P, As, and Sb. F is a fluorine atom, and O is anoxygen atom. t is 2 when M is Si, and t is 1 when M is P, As, or Sb.

X is an oxygen atom or —N(R¹)—. N is a nitrogen atom, and R¹ is ahydrocarbon group having 1 to 10 carbon atoms and optionally having ahetero atom and/or a halogen atom (the hydrocarbon group optionallyhaving a branched-chain or ring structure when the number of carbonatoms is 3 or more).

When X is —N(R¹)—, and p is 0, X and W are directly bonded and may forma structure as shown in at least one selected from the general formulas(2) to (4) below. In the case of the general formula (3) below where thedirect bond is a double bond, R² is not present.

Y is a carbon atom or a sulfur atom. q is 1 when Y is a carbon atom. qis 1 or 2 when Y is a sulfur atom.

W represents a hydrocarbon group having 1 to 10 carbon atoms andoptionally having a hetero atom and/or a halogen atom (the hydrocarbongroup optionally having a branched-chain or ring structure when thenumber of carbon atoms is 3 or more), or —N(R²)—. Here, R² represents ahydrogen atom, an alkaline metal, or a hydrocarbon group having 1 to 10carbon atoms and optionally having a hetero atom and/or a halogen atom.When the number of carbon atoms is 3 or more, R² may have abranched-chain or ring structure.

p is 0 or 1, and q is an integer of 0 to 2, and r is an integer of 0 to2. Further, p+r≥1.

The difluoro ionic complex (1) is a six-coordinate complex in whichbidentate ligands are bidentately coordinated to the central element M,and fluorine atom (hereinafter, referred to as F) is further bidentatelycoordinated. A complex in which a ligand is coordinated to the centralelement M (Si, P, As, Sb) through oxygen atom or nitrogen atom isstable, and very slowly undergoes isomerization due to exchange of theligand in the absence of a catalyst. This can allow for separation oftwo conformational isomers: a cis isomer (1-Cis) in which two fluorineatoms are bonded in the same side when viewed from the central elementand a trans isomer (1-Trans) in which they are bonded in the oppositesides.

A cis/trans mixture will be obtained when concentrating a reactionliquid of the difluoro ionic complex (1) obtained after excessivelypromoting the reaction under a modified version of the conditionsdescribed in Patent Document 6, or a reaction liquid of the difluoroionic complex (1) obtained by fluorinating a three-molecule coordinationproduct synthesized in accordance with Patent Document 5. When themixture are repeatedly crystallized in a mixed solvent of a carbonateester and a chlorinated solvent (both in the filtrate and the motherliquor), (1-Cis) and (1-Trans) each with a purity of 99.9 mol % or morecan be obtained separately. Further, (1-Cis) and (1-Trans) may be eachobtained by selective synthesis. (1-Cis) and (1-Trans) each preferablyhave a purity of 95 mol % or more, more preferably 98 mol % or more, andeven more preferably 99 mol % or more.

A difluoro ionic complex (1) to be added to the electrolytic solutionfor nonaqueous electrolytic solution batteries according to the presentinvention is not a mixture of the equal amount of cis/trans, but thepercentage of (1-Cis) in the difluoro ionic complex (1) to be includedin the electrolytic solution for nonaqueous electrolytic solutionbatteries is 95 mol % or more, preferably 98 mol % or more, and morepreferably 99 mol % or more. That is, the mass ratio (1-Trans)/(1-Cis)of (1-Trans) to (1-Cis) is preferably 0.05 or less even when (1-Trans)is included in the electrolytic solution for nonaqueous electrolyticsolution batteries.

No matter whether the difluoro ionic complex is a cis isomer or a transisomer, a combination of M, X, Y, W, p, q, r, and t in an anion moietyof the difluoro ionic complex (1) is preferably at least one in any ofthe following combinations selected from (1a) to (1d) below.

(1a) M=P; X=O; Y=C; p=q=t=1; and r=0

(1b) M=P; X=O; W=C(CF₃)₂; p=q=0; and r=t=1;

(1c) M=Si; X=O; Y=C; p=q=1; t=2; and r=0

(1d) M=P; X=N(R¹); Y=C; R¹=CH₃; p=q=t=1; and r=0

Further, there is no particular limitation for A % as a cation of thedifluoro ionic complex (1), where A % is any one selected from the groupconsisting of a metal ion, a proton, and an onium ion, as long as itdoes not impair the performance of the nonaqueous electrolytic solutionand the nonaqueous electrolytic solution battery according to thepresent invention, but a lithium ion, a sodium ion, a potassium ion, aquaternary alkylammonium ion, or a combination of at least two thereofis preferred in view of helping ionic conductance in a nonaqueouselectrolytic solution battery. There is no particular limitation for thequaternary alkylammonium ion, but examples includetrimethylpropylammonium and 1-butyl-1-methylpyrrolidinium.

For example, the difluoro ionic complexes (1a-Cis) and (1a-Trans) inwhich A=Li; M=P; X=O; Y=C; p=q=t=1; and r=0 are not readily isomerizedunder neutral conditions. The ratio of (1a-Cis) and (1a-Trans) does notchange at 40° C. after 4 hours in solutions of ethylmethyl carbonatewhere (1a-Cis) and (1a-Trans) are mixed in 1:9 or 5:5.

The nonaqueous electrolytic solution according to the present inventionpreferably contains an electrolyte, a nonaqueous solvent or a polymermixture, and one or more ionic complexes selected from thecis-coordinated ionic complexes represented by the general formula(1-Cis) in an amount of 0.001 mass % or more and 20 mass % or less.Inclusion of (1-Cis) can significantly improve output characteristics(in particular, output characteristics at low temperature after chargeand discharge are repeated). The content of (1-Cis) in the nonaqueouselectrolytic solution is preferably 0.01 mass % or more and 10 mass % orless. More preferably, the content is 0.1 mass % or more and 3.0 mass %or less. A content of less than 0.001 mass % may result in aninsufficient effect for improving output characteristics of a nonaqueouselectrolytic solution battery at low temperature. On the other hand, acontent of more than 20 mass % may excessively increase the viscosity ofan electrolytic solution to interfere with movement of cations in anonaqueous electrolytic solution battery, resulting in decreased batteryperformance.

Further, output characteristics at low temperature after storage at hightemperature can be improved by adding a certain amount of (1-Trans)relative to (1-Cis). At this time, the difluoro ionic complex(1-Trans)/the difluoro ionic complex (1-Cis) (mass ratio) is in a rangeof 0.0001 to 0.05, preferably 0.001 to 0.03, and more preferably 0.002or more and 0.01 or less.

In the present invention, methods of quantifying the mass ratio(1-Trans)/(1-Cis) of (1-Trans) to (1-Cis) in an electrolytic solutioninclude NMR analysis, liquid chromatography-mass spectrometry (LC-MS),and the like. In NMR analysis, (1-Trans) and (1-Cis) each have a peak indifferent positions in NMR, and thus the mass ratio can be quantified bymeasuring the areas of their identified peaks. In LC-MS, the peaks of(1-Trans) and (1-Cis) can be separated using a column, and thus the massratio can be quantified by measuring their peak areas.

Further, addition of the tetrafluoro ionic complex (1-Tetra) havingtetradentate F atoms to a nonaqueous electrolytic solution containing(1-Cis) or (1-Cis)+(1-Trans) can lead to suppression of an increase inthe pressure inside a container when the nonaqueous electrolyticsolution is subjected to long-term storage. At this time, thetetrafluoro ionic complex (1-Tetra)/the difluoro ionic complex (1-Cis)(mass ratio) is in a range of preferably 0.02 to 0.25, more preferably0.05 to 0.22, and even more preferably 0.07 to 0.20.

Further, the group (II) compound above is at least one compound selectedfrom the group consisting of a cyclic phosphazene compound representedby the general formula (II-1) below, a siloxane compound represented bythe general formula (II-2) below, an aromatic compound represented bythe general formula (II-3) below, a cyclohexene compound represented bythe general formula (II-4) below, a phosphoric acid ester compoundrepresented by the general formula (II-5) below, a fluorinated linearether compound represented by the general formula (II-6) below, afluorinated cyclic ether compound represented by the general formula(II-7) below, and a boric acid ester compound represented by the generalformula (II-8) below. These may be used alone, or may be used byappropriately combining two or more.

[In the general formula (II-1), R¹ to R⁶ are each independently asubstituent selected from the group consisting of a halogen atom, anamino group, an alkyl group having 1 to 10 carbon atoms, an alkoxy grouphaving 1 to 10 carbon atoms, and an aryloxy group having 6 to 12 carbonatoms; n¹ is an integer of 1 to 10; and the alkyl group, the alkoxygroup, and the aryloxy group optionally have a hetero atom and/or ahalogen atom;

in the general formula (II-2), R⁷ to R¹² are each independently asubstituent selected from the group consisting of an alkyl group having1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, analkenyl group having 2 to 10 carbon atoms, an alkenyloxy group having 2to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, analkynyloxy group having 2 to 10 carbon atoms, an aryl group having 6 to12 carbon atoms, and an aryloxy group having 6 to 12 carbon atoms, saidgroups optionally having a hetero atom and/or a halogen atom; n² is aninteger of 1 to 10; when n² is 2 or more, R¹¹'s and R¹²'s independentlyare optionally the same as or different from one another; a grouprepresented by OR⁷ and a group represented by OR⁸ are optionally bondedto each other to form a siloxane bond; and the siloxane compoundrepresented by the general formula (II-2) includes a siloxane compoundrepresented by the general formula (II-2′); and

in the general formula (II-2′), R¹³ and R¹⁴ are each independently asubstituent selected from the group consisting of an alkyl group having1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, analkenyl group having 2 to 10 carbon atoms, an alkenyloxy group having 2to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, analkynyloxy group having 2 to 10 carbon atoms, an aryl group having 6 to12 carbon atoms, and an aryloxy group having 6 to 12 carbon atoms, saidgroups optionally having a hetero atom and/or a halogen atom; n³ is aninteger of 2 to 10; R¹³'s and R¹⁴'s independently are optionally thesame as or different from one another.]

[In the general formula (II-3), R¹⁵ to R²⁰ are each independently asubstituent selected from the group consisting of a hydrogen atom, ahalogen atom, and a hydrocarbon group having 1 to 12 carbon atoms; andat least two of R¹⁵ to R²⁰ are optionally bonded to one another to forma ring; and in the general formula (II-4), R²¹ to R²⁴ are eachindependently a substituent selected from the group consisting of ahydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 12carbon atoms; and at least two of R²¹ to R²⁴ are optionally bonded toone another to form a ring.]

[In the general formula (II-5), R²⁵ to R²⁷ are each independently asubstituent selected from the group consisting of an alkyl group having1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, analkenyl group having 2 to 10 carbon atoms, a cyano group, an aminogroup, a nitro group, an alkoxy group having 1 to 10 carbon atoms, and acycloalkyl group having 3 to 10 carbon atoms, said groups optionallyhaving a hetero atom and/or a halogen atom; and any two or all of R²⁵,R²⁶, and R²⁷ are optionally bonded to one another to form a ringstructure;

in the general formula (II-6), R²⁸ and R²⁹ are each independently asubstituent selected from the group consisting of an alkyl group having1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, afluorinated alkyl group having 1 to 10 carbon atoms, a fluorinatedcycloalkyl group having 3 to 10 carbon atoms, an alkyl group having 1 to10 carbon atoms and having an ethereal oxygen atom between the carbonatoms, and a fluorinated alkyl group having 1 to 10 carbon atoms andhaving an ethereal oxygen atom between the carbon atoms; and at leastone of R²⁸ and R²⁹ contains a fluorine atom;

in the general formula (II-7), R³² is a substituent selected from thegroup consisting of an alkylene group having 1 to 5 carbon atoms, afluorinated alkylene group having 1 to 5 carbon atoms, an alkylene grouphaving 1 to 5 carbon atoms and having an ethereal oxygen atom betweenthe carbon atoms, and a fluorinated alkylene group having 1 to 5 carbonatoms and having an ethereal oxygen atom between the carbon atoms; R³⁰and R³¹ are each independently a substituent selected from the groupconsisting of an alkyl group having 1 to 10 carbon atoms, a cycloalkylgroup having 3 to 10 carbon atoms, a fluorinated alkyl group having 1 to10 carbon atoms, a fluorinated cycloalkyl group having 3 to 10 carbonatoms, an alkyl group having 1 to 10 carbon atoms and having an etherealoxygen atom between the carbon atoms, and a fluorinated alkyl grouphaving 1 to 10 carbon atoms and having an ethereal oxygen atom betweenthe carbon atoms; and at least one of R³¹ and R³² contains a fluorineatom; and

in the general formula (II-8), R³³ to R³⁵ are each independently afluorinated alkyl group having 1 to 10 carbon atoms.]

The content of the group (II) compound is preferably in the range of0.01 mass % or more and 50 mass % or less relative to the nonaqueouselectrolytic solution.

In the case where the compound shown in the (II) above comprises acyclic phosphazene compound represented by the general formula (II-1)above, the content of the cyclic phosphazene compound represented by thegeneral formula (II-1) above is preferably in the range of 0.5 mass % ormore and 15 mass % or less relative to the nonaqueous electrolyticsolution. In the case where the addition of the cyclic phosphazenecompound represented by the general formula (II-1) above is for thepurpose of prevention of expansion, the content thereof is preferably inthe range of 0.5 mass % or more and 10 mass % or less relative to thenonaqueous electrolytic solution. In the case where the addition is forthe purpose of flame retardant, the content thereof is preferably in therange of 5 mass % or more and 15 mass % or less relative to thenonaqueous electrolytic solution.

In the case where the compound shown in the (II) above comprises asiloxane compound represented by the general formula (II-2) above, thecontent of the siloxane compound represented by the general formula(II-2) above is preferably in the range of 0.01 mass % or more and 10mass % or less relative to the nonaqueous electrolytic solution.

In the case where the compound shown in the (II) above comprises anaromatic compound represented by the general formula (II-3) above, thecontent of the aromatic compound represented by the general formula(II-3) above is preferably in the range of 0.01 mass % or more and 10mass % or less relative to the nonaqueous electrolytic solution.

In the case where the compound shown in the (II) above comprises acyclohexene compound represented by the general formula (II-4) above,the content of the cyclohexene compound represented by the generalformula (II-4) above is preferably in the range of 0.01 mass % or moreand 10 mass % or less relative to the nonaqueous electrolytic solution.

In the case where the compound shown in the (II) above comprises aphosphoric acid ester compound represented by the general formula (II-5)above, the content of the phosphoric acid ester compound represented bythe general formula (II-5) above is preferably in the range of 5 mass %or more and 40 mass % or less relative to the nonaqueous electrolyticsolution.

In the case where the compound shown in the (II) above comprises afluorinated linear ether compound represented by the general formula(II-6) above, the content of the phosphoric acid ester compoundrepresented by the general formula (II-6) above is preferably in therange of 10 mass % or more and 50 mass % or less relative to thenonaqueous electrolytic solution.

In the case where the compound shown in the (II) above comprises afluorinated cyclic ether compound represented by the general formula(II-7) above, the content of the fluorinated cyclic ether compoundrepresented by the general formula (II-7) above is preferably in therange of 10 mass % or more and 50 mass % or less relative to thenonaqueous electrolytic solution.

In the case where the compound shown in the (II) above comprises a boricacid ester compound represented by the general formula (II-8) above, thecontent of the boric acid ester compound represented by the generalformula (II-8) above is preferably in the range of 3 mass % or more and30 mass % or less relative to the nonaqueous electrolytic solution.

Examples of the cyclic phosphazene compound represented by the generalformula (II-1) above include the following compounds. Addition of thecyclic phosphazene compound represented by the general formula (II-1)enables imparting mainly expansion-preventing effects and/or flameretardancy to the electrolytic solution. However, the cyclic phosphazenecompound represented by the general formula (II-1) used in the presentinvention is not at all limited by the following examples.

Examples of the siloxane compound represented by the general formula(II-2) above include the following compounds. Addition of the siloxanecompound represented by the general formula (II-2) enables impartingmainly expansion-preventing effects to the electrolytic solution.

Examples of the aromatic compound represented by the general formula(II-3) above include the following compounds. Addition of the aromaticcompound represented by the general formula (II-3) enables impartingmainly overcharging-preventing effects to the electrolytic solution.

Examples of the cyclohexene compound represented by the general formula(II-4) above include the following compounds. Addition of thecyclohexene compound represented by the general formula (II-4) enablesimparting mainly overcharging-preventing effects to the electrolyticsolution.

Examples of the phosphoric acid ester compound represented by thegeneral formula (II-5) above include the following compounds. Additionof the phosphoric acid ester compound represented by the general formula(II-5) enables imparting mainly flame-retardant effects to theelectrolytic solution.

Examples of the fluorinated linear ether compound represented by thegeneral formula (II-6) above include the following compounds. Additionof the fluorinated linear ether compound represented by the generalformula (II-6) enables imparting mainly flame-retardant effects to theelectrolytic solution.CF₃CH₂OCF₂CF₂H   (II-6-1)CF₃CH₂OCF₂CFHCF₃   (II-6-2)CHF₂CF₂CH₂OCF₂CFHCF₃   (II-6-3)

Examples of the fluorinated cyclic ether compound represented by thegeneral formula (II-7) above include the following compounds. Additionof the fluorinated cyclic ether compound represented by the generalformula (II-7) enables imparting mainly flame-retardant effects to theelectrolytic solution.

Examples of the boric acid ester compound represented by the generalformula (II-8) above include the following compounds. Addition of theboric acid ester compound represented by the general formula (II-8)enables imparting mainly flame-retardant effects to the electrolyticsolution.

Further, addition of the tetrafluoro ionic complex (1-Tetra) havingtetradentate F atoms to a nonaqueous electrolytic solution containing(1-Cis) or (1-Cis)+(1-Trans) can lead to suppression of an increase inthe pressure inside a container when the nonaqueous electrolyticsolution is subjected to long-term storage. At this time, thetetrafluoro ionic complex (1-Tetra)/the difluoro ionic complex (1-Cis)(mass ratio) is in a range of preferably 0.02 to 0.25, more preferably0.05 to 0.22, and even more preferably 0.07 to 0.20.

In the general formula (1-Tetra), A⁺, M, F, O, X, Y, W, p, q, r, and tare as described in the general formula (1).

A combination of M, X, Y, W, p, q, r, and t in the anion moiety of thetetrafluoro ionic complex (1-Tetra) is preferably at least onecombination selected from (Tetra-a), (Tetra-b), (Tetra-c), and (Tetra-d)below.

(Tetra-a) M=P; X=O; Y=C; p=q=t=1; and r=0

(Tetra-b) M=P; X=O; W=C(CF₃)₂; p=q=0; and r=t=1

(Tetra-c) M=Si; X=O; Y=C; p=q=1; t=2; and r=0

(Tetra-d) M=P; X=N(R¹); Y=C; R¹=CH₃; p=q=t=1; and r=0

It is noted that a low-temperature property (the ratio of dischargecapacities of −20° C./25° C.) at 0° C. or below as well as cyclecharacteristics and high-temperature storage properties is improved whenan electrolytic solution including both an ionic complex (1-Tetra) wherethe anion moiety is (Tetra-a) and A=Li (hereinafter referred to as(5a-Tetra)) and an ionic complex (1-Cis) where the anion moiety is(Cis-a) and A=Li (hereinafter referred to as (1a-Cis)) is used. Further,the tetrafluoro ionic complex (1-Tetra) does not have conformationalisomers.

Although a six-coordinate ionic complex having two types of ligands (oneof them is F) which can be present as its cis- or trans-isomer as shownin the difluoro ionic complex (1) has been used as described in PatentDocument 6, the effects of the cis isomer alone and the trans isomeralone have not closely studied separately. In the present application, acis isomer alone or a trans isomer alone was separately added to comparetheir individual effects. Results revealed that the cis isomer showed abetter effect for improving output characteristics at low temperatureafter cycle durability tests.

When voltage is applied to a nonaqueous electrolytic solution containinga difluorophosphate complex having P as the central element selectedfrom the difluoro ionic complexes (1), the difluorophosphate complex isreductively decomposed to generate a reduction-reaction decompositionproduct (intermediate) with a very short life time in the system. It mayreact with a functional group present on the surface of a negativeelectrode to form a SEI on the negative electrode. The SEI mainlyincludes a derivative of difluorophosphoric acid and a derivative ofcarbonic acid.

Reduction-reaction decomposition products from reduction reactions arelikely different between the cis isomer and the trans isomer due tosteric and electronic factors, resulting in different selectivities andrates for a reaction with a functional group on the surface of anelectrode.

First, steric factors will be discussed with regard to the initiation ofa reduction reaction between a negative electrode and difluorophosphatecomplexes (cis, trans). A difluorophosphate complex receives an electronfrom a negative electrode at a portion of a ligand other than F (forexample, a carbon atom on the carbonyl group in the case of 1a) wherethe reduction reaction is initiated. Accordingly, the electron needs toapproach the negative electrode from a side where F is not bonded toinitiate the reduction reaction. The trans isomer has F atoms bonded atthe upper and lower sides of the molecule. Consequently, the reductionreaction is initiated only when an electron approaches an electrode fromeither right or left, i.e., from a range of total 180° in the horizontaldirection except for 180° in the vertical direction. In contrast, thecis isomer has F atoms only in the same side, and thus an electron canapproach from a range of 200° to 250° in the opposite side. Thisincreases the probability of initiation of the reduction reaction ascompared with the trans isomer.

Next, electronic factors will be discussed. The LUMO level is slightlylower for the cis isomer than for the trans isomer. Therefore, the cisisomer more readily receives an electron from an electrode, leading to amore rapidly proceeding reduction reaction.

Further, the difluorophosphate complex before decomposition is asix-coordinate phosphorus compound while the difluoro phosphoric acidderivative as the main component of SEI after decomposition is afive-coordinate phosphorus compound. It undergoes transform fromsix-coordination to five-coordination when the difluorophosphate complexdecomposes to generate a highly active intermediate, and theintermediate reacts with a functional group on the surface of a negativeelectrode. For the trans isomer, the bond angle of F—P—F beforedecomposition (six-coordination) is 180° while the bond angle of F—P—Fafter decomposition (five-coordination) is about 100°. Therefore, alarge structural change is required. On the other hand, the cis isomershows only a small change of from 90° (before decomposition,six-coordination) to about 100° (after decomposition,five-coordination). As clearly understood from the above, the energyrequired for the transition state of the reductive decompositionreaction is smaller in the cis isomer without a large structural change,and thus the reductive decomposition of the cis isomer is more favoredthan that of the trans isomer. This is not limited to a complex havingphosphorus as the central element, but also can be applied to arsenic,antimony, and silicon.

Considering that the reductive decomposition reaction proceeds indifferent rates between the cis isomer and the trans isomer, thedifference in the performance of SEI formed therefrom will be discussed.

The reductive decomposition reaction rapidly proceeds in the cis isomerto rapidly form an SEI which mainly contains a derivative ofdifluorophosphoric acid and a derivative of carbonic acid. To date, ithas been revealed that an SEI consisting of a derivative ofdifluorophosphoric acid has an excellent effect for improving the cyclecharacteristics, high-temperature storage properties, and outputcharacteristics of a battery while an SEI consisting of a derivative ofcarbonic acid has an excellent effect for improving the cyclecharacteristics and high-temperature storage properties. The reductivedecomposition reaction of the trans isomer is slower as compared withthat of the cis isomer, and thus prompt formation of an SEI consistingonly of a derivative of difluorophosphoric acid and a derivative ofcarbonic acid is difficult to obtain. Due to this, the reductionreaction of a solvent also proceeds concomitantly with it, resulting information of an SEI mainly containing a mixture of a derivative ofdifluorophosphoric acid and a derivative of carbonic acid from thedifluorophosphate complex, and carbonic acid and an alkyl carbonate saltfrom a solvent. (the difluorophosphate complex is much more susceptibleto decomposition than a solvent, but the number of solvent molecules isenormously large, and thus decomposition of a solvent also proceedsalthough it is very little.)

An SEI consisting of an alkyl carbonate salt included therein canimprove cycle characteristics and high-temperature storage properties,but may decrease cation conductivity as compared with an SEI consistingof a derivative of carbonic acid due to a reduced ratio of oxygen.Therefore, output characteristics may be improved only marginally, ormay even be decreased.

As described above, the different rates of the reductive decompositionreaction between the cis isomer and the trans isomer may alter theselectivity of the reductive decomposition reaction (the presence orabsence of solvent decomposition), resulting in different maincomponents in SEIs formed therefrom. This is likely responsible for thedifference in the effects of SEIs for improving the battery performancein the end.

As described above, output characteristics at low temperature afterhigh-temperature storage can be improved by adding (1-Trans) in acertain amount relative to (1-Cis). The reasons of this will bediscussed similarly in terms of the different properties of SEIs betweenthe cis isomer and the trans isomer. In a lithium battery, lithium isgradually released from a negative electrode in a fully chargedcondition to react with a solvent during high-temperature storage asoxidative decomposition of the solvent proceeds on the surface of apositive electrode maintained at a high potential. Due to this, highlyresistive decomposition products accumulate on the positive and negativeelectrodes. Further, reversibly available lithium is decreased,resulting in decreased battery performance (the charge-and-dischargerate and capacity are decreased). A negative-electrode SEI consisting ofan alkyl carbonate salt has a low ionic conductivity, and thus isdisadvantageous for output characteristics. However, it can reduce therelease of lithium from the negative electrode during high-temperaturestorage to prevent a decreased capacity after high-temperature storage.As a result, a high capacity is maintained after high-temperaturestorage. When high-rate discharge capacities (output characteristics) atlow temperature are compared after high-temperature storage, the amountof electricity obtained at high-rate discharge as compared with low-ratedischarge is lower as compared with an electrolytic solution of (1-Cis)only. However, the absolute values of the amount of electricity obtainedat high-rate discharge is higher for an electrolytic solution having acertain amount of (1-Trans) relative to (1-Cis) than an electrolyticsolution having (1-Cis) only because the starting capacity is higher.

In the tetrafluoro ionic complex (1-Tetra) having tetradentate F atoms,a ligand other than F has lower electron density as compared with thedifluoro ionic complex (1) having bidentate F atoms because of thestrong electron-withdrawing effect of F. This makes the ligand moresusceptible to a nucleophilic attack. Therefore, if a trace amount ofwater is present in an electrolytic solution, (1-Tetra) is selectivelyhydrolyzed instead of (1). For example, when the central element M is P,the moiety of tetrafluorophosphoric acid of (1-Tetra) is converted intoa salt of hexafluorophosphoric acid by hydrolysis (a ligand other than Fis disproportioned after leaving). The ligand moiety other than F leavesfrom the central element P, and is decomposed to release carbon dioxideand carbon monoxide. The amount of carbon dioxide and carbon monoxidereleased at this time is ½ mol equivalent relative to (1). This cansignificantly reduce the yield of carbon dioxide and carbon monoxidewhich otherwise may increase the internal pressure.

In general, a nonaqueous electrolytic solution is called a nonaqueouselectrolyte when a nonaqueous solvent is used, and called a polymericsolid electrolyte when a polymer is used. Polymeric solid electrolytesinclude those containing a nonaqueous solvent as a plasticizing agent.It is noted that an electrochemical device is referred to as anonaqueous electrolytic solution battery, the device including thepresent nonaqueous electrolytic solution; a negative-electrode materialenabling reversible insertion and desorption of an alkali metal ion suchas a lithium ion and a sodium ion or an alkaline earth metal ion; and apositive-electrode material enabling reversible insertion and desorptionof an alkali metal ion such as a lithium ion and a sodium ion or analkaline earth metal ion.

There is no particular limitation for the electrolyte, and salts of anycations and any anions can be used. As specific examples, cationsinclude alkali metal ions such as a lithium ion, a sodium ion, andpotassium ion; alkaline earth metal ions; quaternary ammonium ions; andthe like. Anions include anions of hexafluorophosphoric acid,tetrafluoroboric acid, perchloric acid, hexafluoroarsenic acid,hexafluoroantimonic acid, trifluoromethanesulfonic acid,bis(trifluoromethanesulfonyl)imide, bis(pentafluoroethanesulfonyl)imide,(trifluoromethanesulfonyl) (pentafluoroethanesulfonyl)imide,bis(fluorosulfonyl)imide, (trifluoromethanesulfonyl)(fluorosulfonyl)imide, (pentafluoroethanesulfonyl)(fluorosulfonyl)imide, tris (trifluoromethanesulfonyl)methide,bis(difluorophosphonyl)imide, and the like. These electrolytes may beused alone, or may be used in a mixture in any combination or ratio oftwo or more depending on applications. Among these, cations of lithium,sodium, magnesium, and quaternary alkylammonium are preferred ascations, and anions of hexafluorophosphoric acid, tetrafluoroboric acid,bis(trifluoromethane sulfonyl)imide, bis(fluorosulfonyl)imide, andbis(difluoro phosphonyl)imide are preferred as anions in view of energydensity, output characteristics, lifetime, and the like of a battery.

There is no particular limitation for the nonaqueous solvent as long asit is an aprotic solvent in which the ionic complex according to thepresent invention can be dissolved. For example, carbonates, esters,ethers, lactones, nitriles, imides, sulfones, and the like can be used.Further, they may be used alone or as a mixed solvent of two or more.Specific examples can include ethylmethyl carbonate, dimethyl carbonate,diethyl carbonate, methylpropyl carbonate, ethylpropyl carbonate,methylbutyl carbonate, ethylene carbonate, propylene carbonate, butylenecarbonate, methyl acetate, ethyl acetate, methyl propionate, ethylpropionate, diethyl ether, acetonitrile, propionitrile, tetrahydrofuran,2-methyltetrahydrofuran, furan, tetrahydropyran, 1,3-dioxane,1,4-dioxane, dibutyl ether, diisopropyl ether, 1,2-dimethoxyethane,N,N-dimethylformamide, dimethyl sulfoxide, sulfolane, γ-butyrolactone,γ-valerolactone, and the like.

Further, the nonaqueous solvent preferably contains at least oneselected from the group consisting of cyclic carbonates and chaincarbonates. Examples of cyclic carbonates can include ethylene carbonateand propylene carbonate, and examples of chain carbonates can includeethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, andmethylpropyl carbonate.

Further, in addition to carbonates, the nonaqueous solvent may furthercontain at least one selected from the group consisting of esters,ethers, lactones, nitriles, amides, and sulfones.

Further, the nonaqueous solvent may further contain at least onecompound selected from the group consisting of vinylene carbonate,vinylethylene carbonate, ethynylethylene carbonate, and fluoroethylenecarbonate.

There is no particular limitation for the polymer which can be used toobtain a polymeric solid electrolyte including the ionic complexaccording to the present invention as long as it is an aprotic polymerin which the aforementioned ionic complexes and the aforementionedelectrolyte can be solved. Examples can include polymers havingpolyethylene oxide in their main chains or side chains, homopolymers orcopolymers of polyvinylidene fluoride, methacrylate ester polymers,polyacrylonitrile, and the like. When a plasticizing agent is added tothese polymers, the above aprotic nonaqueous solvents may be used.

In the present invention, there is no particular limitation for theconcentration of a electrolyte in these ion conductors, but the lowerlimit is preferably 0.5 mol/L or more, more preferably 0.7 mol/L ormore, and even more preferably 0.9 mol/L or more, and the upper limit ispreferably 5.0 mol/L or less, more preferably 4.0 mol/L or less, andeven more preferably 2.0 mol/L or less. A concentration of less than 0.5mol/L may decrease cycle characteristics and output characteristics of anonaqueous electrolytic solution battery due to decreased ionconductivity. On the other hand, a concentration of more than 5.0 mol/Lmay increase the viscosity of a nonaqueous electrolytic solution,decreasing cycle characteristics and output characteristics of anonaqueous electrolytic solution battery again due to decreased ionconductivity.

When a lithium salt is dissolved in manufacture of a nonaqueouselectrolytic solution, the solution temperature of the nonaqueouselectrolytic solution is controlled at 40° C. or below. This can preventgeneration of free acid such as hydrogen fluoride (HF) which may beproduced when a lithium salt in a nonaqueous electrolytic solutionreacts with water in the system to undergo decomposition. As a result,decomposition of a nonaqueous solvent can also be prevented. Therefore,deterioration of the nonaqueous electrolytic solution can be preventedeffectively. Further, in the step of dissolving a lithium salt, thelithium salt is added in small portions until the concentration of theentire lithium salt becomes 0.5 to 4.0 mol/L to prepare a solution. Thiscan prevent generation of free acids such as HF in a similar manner.

For example, the following are preferably performed to maintain thesolution temperature at 40° C. or below. A portion in a range of 10 to35 mass % of the entire lithium salt is first added and dissolved in anonaqueous solvent, and another portion in a range of 10 to 35 mass % ofthe entire lithium salt is then added and dissolved. This operation isrepeated for 2 to 9 times, and then finally the remaining lithium saltis gradually added and dissolved.

In particular, when the nonaqueous electrolytic solution according tothe present invention is prepared, an increased solution temperature ofthe nonaqueous electrolytic solution during preparation may promote theaforementioned side reactions. Therefore, deterioration of thenonaqueous electrolytic solution can be prevented by preventing anincrease in temperature so that the solution temperature of thenonaqueous electrolytic solution is controlled at 40° C. or below. Thiscan assure the quality of the nonaqueous electrolytic solution.

Further, a common additive may be added in any ratio to the nonaqueouselectrolytic solution according to the present invention unless thespirit of the present invention is impaired. Specific examples caninclude compounds having effects for preventing overcharging, forforming a film on a negative-electrode, and for protecting a positiveelectrode such as cyclohexylbenzene, biphenyl, tert-butylbenzene,tert-amylbenzene, biphenyl, o-terphenyl, 4-fluorobiphenyl,fluorobenzene, 2,4-difluorobenzene, difluoroanisole, 1,3-propanesultone,1,3-propenesultone, methylenemethane disulfonate, dimethylenemethanedisulfonate, and trimethylenemethane disulfonate. Further, thenonaqueous electrolytic solution can be used after solidified with agelatinizing agent or a crosslinked polymer as used in a nonaqueouselectrolytic solution battery called a polymer battery.

<2. Nonaqueous Electrolytic Solution Battery>

The nonaqueous electrolytic solution battery according to the presentinvention includes (a) the present nonaqueous electrolytic solution, (b)a positive electrode, (c) a negative electrode, and (d) a separator andis particularly preferably a secondary battery.

[(a) Present Nonaqueous Electrolytic Solution

The nonaqueous electrolytic solution battery according to the presentinvention includes the nonaqueous electrolytic solution as described in<1. Nonaqueous electrolytic solution>.

[(b) Positive Electrode]

(b) the positive electrode preferably includes at least one of oxide andpolyanion compound as a positive-electrode active material.

[Positive-Electrode Active Material]

For a lithium-ion secondary battery in which cations in an nonaqueouselectrolytic solution are mostly lithium ions, there is no particularlimitation for the positive-electrode active material for a positiveelectrode as long as it is capable of charge and discharge, but examplesof it include at least one selected from the group consisting of (A) alithium-transition metal composite oxide having a layer structure andcontaining at least one metal of nickel, manganese, and cobalt; (B) alithium-manganese composite oxide having the spinel structure; (C) alithium-containing olivine-type phosphate salt; and (D) a lithium-richlayered transition metal oxide having the stratified rock-saltstructure.

((A) Lithium-Transition Metal Composite Oxide)

Examples of (A) the lithium-transition metal composite oxide having alayer structure and containing at least one metal of nickel, manganese,and cobalt include lithium-cobalt composite oxides, lithium-nickelcomposite oxides, lithium-nickel-cobalt composite oxides,lithium-nickel-cobalt-aluminum composite oxides,lithium-cobalt-manganese composite oxides, lithium-nickel-manganesecomposite oxides, lithium-nickel-manganese-cobalt composite oxides, andthe like. Those in which some of the main transition metal atoms ofthese lithium-transition metal composite oxides are replaced with otherelements such as Al, Ti, V, Cr, Fe, Cu, Zn, Mg, Ga, Zr, Si, B, Ba, Y,and Sn can also be used.

Specific examples of lithium-cobalt composite oxides and lithium-nickelcomposite oxides can include LiCoO₂, LiNiO₂, and lithium cobalt oxideshaving a hetero element such as Mg, Zr, Al, and Ti(LiCo_(0.98)Mg_(0.01)Zr_(0.01)O₂, LiCo_(0.98)1 Mg_(0.01)Al_(0.01)O₂,LiCo_(0.975)Mg_(0.01)Zr_(0.005)Al_(0.01)O₂, and the like). Lithiumcobalt oxides having a rare earth compound adhered on the surface asdescribed in WO2014/034043 may also be used. Further, those in which aportion of the particle surface of LiCoO₂ particulate powder is coatedwith aluminum oxide as described in Japanese Unexamined PatentApplication, Publication No. 2002-151077 and others may be used.

Lithium-nickel-cobalt composite oxides andlithium-nickel-cobalt-aluminum composite oxides may be represented bythe general formula (1-1).Li_(a)Ni_(1-b-c)Co_(b)M¹ _(c)O₂  (1-1)

In the formula (1-1), M¹ is at least one element selected from Al, Fe,Mg, Zr, Ti, and B, and a is 0.9≤a≤1.2, and b and c satisfy therequirements of 0.1≤b≤0.3 and 0≤c≤0.1, respectively.

These can be prepared in accordance with, for example, the method ofmanufacture as described in Japanese Unexamined Patent Application,Publication No. 2009-137834 and others. Specific examples includeLiNi_(0.8)Co_(0.2)O₂, LiNi_(0.85)Co_(0.10)Al_(0.05)O₂,LiNi_(0.87)Co_(0.10)Al_(0.03)O₂, LiNi_(0.6)CO_(0.3)Al_(0.1)O₂, and thelike.

Specific examples of lithium-cobalt-manganese composite oxides andlithium-nickel-manganese composite oxides include LiNi_(0.5)Mn_(0.5)O₂,LiCo_(0.5)Mn_(0.5)O₂, and the like.

Lithium-nickel-manganese-cobalt composite oxides includelithium-containing composite oxides represented by the general formula(1-2).Li_(d)Ni_(e)Mn_(f)Co_(g)M² _(h)O₂  (1-2)

In the formula (1-2), M² is at least one element selected from Al, Fe,Mg, Zr, Ti, B, and Sn, and d is 0.9≤d≤1.2, and e, f, g, and h satisfythe requirements of e+f+g+h=1, 0≤e≤0.7, 0≤f≤0.5, 0≤g≤0.5, and h≥0.

Preferred are lithium-nickel-manganese-cobalt composite oxidescontaining manganese in the range specified in the general formula (1-2)in order to improve structural stability and high-temperature safety ofa lithium secondary battery. In particular, more preferred is thosefurther containing cobalt in the range specified in the general formula(1-2) in order to improve high-rate properties of a lithium-ionsecondary battery.

Specific examples include Li[Ni_(1/3)Mn_(1/3)CO_(1/3)]O₂,Li[Ni_(0.45)Mn_(0.35)CO_(0.2)]O₂, Li[Ni_(0.5)Mn_(0.3)CO_(0.2)]O₂,Li[Ni_(0.6)Mn_(0.2)Co_(0.2)]O₂,Li[Ni_(0.49)Mn_(0.3)CO_(0.2)Zr_(0.01)]O₂,Li[Ni_(0.49)Mn_(0.3)Co_(0.2)Mg_(0.01)]O₂, and the like, which have acharge-discharge range, for example, at 4.3 V or above.

((B) Lithium-Manganese Composite Oxide Having the Spinel Structure)

Examples of (B) the lithium-manganese composite oxide having the spinelstructure include a spinel-type lithium-manganese composite oxiderepresented by the general formula (1-3).Li_(j)(Mn_(2-k)M³ _(k))O₄  (1-3)

In the formula (1-3), M³ is at least one metal element selected from Ni,Co, Fe, Mg, Cr, Cu, Al, and Ti, and j is 1.05≤j≤1.15, and k is 0≤k≤0.20.

Specific examples include LiMn₂O₄, LiMn_(1.95)Al_(0.05)O₄,LiMn_(1.9)Al_(0.1)O₄, LiMn_(1.9)Ni_(0.1)O₄, and LiMn_(1.5)Ni_(0.5)O₄,and the like.

((C) Lithium-Containing Olivine-Type Phosphate Salt)

Examples of (C) the lithium-containing olivine-type phosphate saltinclude those represented by the general formula (1-4).LiFe_(1-n)M⁴ _(n)PO₄  (1-4)

In the formula (1-4), M⁴ is at least one selected from Co, Ni, Mn, Cu,Zn, Nb, Mg, Al, Ti, W, Zr, and Cd, and n is 0≤n≤1.

Specific example include LiFePO₄, LiCoPO₄, LiNiPO₄, LiMnPO₄, and thelike. Among these, LiFePO₄ and/or LiMnPO₄ are preferred.

((D) Lithium-Rich Layered Transition-Metal Oxide)

Examples of (D) the lithium-rich layered transition-metal oxide havingthe stratified rock-salt structure include those represented by thegeneral formula (1-5).xLiM⁵O₂.(1−x)Li₂M⁶O₃  (1-5)

In the formula (1-5), x is a number satisfying 0<x<1, and M⁵ is at leastone metal element having a mean oxidation number of 3⁺, and M⁶ is atleast one metal element having a mean oxidation number of 4⁺. In theformula (1-5), M⁵ is at least one metal element selected from Mn, Ni,Co, Fe, V, and Cr preferably having a valence of 3. That valence may bea mean oxidation number of 3 where a metal with a valence of 2 and ametal with a valence of 4 are used in the equivalent amount.

Further, in the formula (1-5), M⁶ is preferably one or more metalelements selected from Mn, Zr, and Ti. Specific examples include0.5[LiNi_(0.5)Mn_(0.5)O₂].0.5[Li₂MnO₃],0.5[LiNi_(2/3)CO_(1/3)Mn_(1/3)O₂].0.5[Li₂MnO₃],0.5[LiNi_(0.375)Co_(0.25)Mn_(0.375)O₂].0.5[Li₂MnO₃],0.5[LiNi_(0.375)Co_(0.125)Fe_(0.125)Mn_(0.375)O₂].0.5[Li₂MnO₃],0.45[LiNi_(0.375)Co_(0.25)Mn_(0.375)O₂].0.10[Li₂TiO₃].0.45[Li₂MnO₃], andthe like.

The positive-electrode active material (D) represented by the generalformula (1-5) is known to have a high capacity in high-voltage chargingat 4.4 V or more (in terms of Li) (for example, see U.S. Pat. No.7,135,252).

These positive-electrode active materials can be prepared in accordancewith the methods of manufacture and others described in, for exampleJapanese Unexamined Patent Application, Publication No. 2008-270201,WO2013/118661, Japanese Unexamined Patent Application, Publication No.2013-030284, and the like.

The positive-electrode active material needs to contain at least oneselected from (A) to (D) described above as the main component. Examplesof other additives which may be added include, for example, transitionelement chalcogenides such as FeS₂, TiS₂, V₂O₅, MoO₃, and MoS₂; orelectrically conductive polymers such as polyacethylene,poly(p-phenylene), polyaniline, and polypyrrole; activated carbon;radical-generating polymers; carbon materials; and the like.

[Positive-Electrode Current Collector]

The positive electrode has a positive-electrode current collector. Asthe positive-electrode current collector, for example, aluminum,stainless steel, nickel, titanium, or alloys thereof can be used.

[Positive-Electrode Active-Material Layer]

In the positive electrode, for example, a positive-electrodeactive-material layer is formed on at least one surface of thepositive-electrode current collector. The positive-electrodeactive-material layer includes, for example, the aforementionedpositive-electrode active material, a binding agent, and, if desired, anelectrically conductive agent.

Examples of the binding agent include polytetrafluoroethylene,poly(vinylidene fluoride), a styrene-butadiene rubber (SBR) resin, orthe like.

As the electrically conductive agent, for example, carbon materials canbe used such as acetylene black, Ketjen black, carbon fiber, or graphite(granular graphite and flaky graphite). Acetylene black and Ketjen blackwith low crystallinity are preferably used for the positive electrode.

[(c) Negative Electrode]

The negative electrode preferably includes at least one of thenegative-electrode active materials below.

[Negative-Electrode Active Material]

For a lithium-ion secondary battery in which cations in an nonaqueouselectrolytic solution are mostly lithium ions, examples of thenegative-electrode active material of the negative electrode include,for example, those capable of doping/de-doping lithium ions whichcontain, for example, at least one selected from (E) a carbon materialhaving a d value of the lattice plane [002] of 0.340 nm or less asdetermined by X ray diffraction; (F) a carbon material having a d valueof the lattice plane [002] of more than 0.340 nm as determined by X raydiffraction; (G) an oxide of one or more metals selected from Si, Sn,and Al; (H) one or more metals selected from Si, Sn, and Al, and analloy comprising the one or more metals and further comprising or notcomprising lithium; and (I) a lithium titanium oxide. Thesenegative-electrode active materials may be used alone or in combinationof two or more.

((E) Carbon Material Having a d Value of the Lattice Plane [002] of0.340 nm or Less as Determined by X Ray Diffraction)

Examples of (E) the carbon material having a d value of the latticeplane [002] of 0.340 nm or less as determined by X ray diffractioninclude pyrolytic carbons, cokes (for example, pitch coke, needle coke,petroleum coke, and the like), graphites, calcined products of organicpolymer compounds (for example, those obtained by calcining andcarbonizing a phenol resin, a furan resin, and the like at anappropriate temperature), carbon fiber, and activated carbon. These maybe graphitized. The above carbon materials preferably have aninterplanar spacing (d002) of the plane [002] of 0.340 nm or less asmeasured by the X-ray diffraction method. In particular, preferred is agraphite having a true density of 1.70 g/cm³ or more or ahigh-crystallinity carbon material having characteristics similar tothat.

((F) Carbon Material Having a d Value of the Lattice Plane [002] of Morethan 0.340 nm as Determined by X Ray Diffraction)

Examples of (F) the carbon material having a d value of the latticeplane [002] of more than 0.340 nm as determined by X ray diffractioninclude amorphous carbon, which is a carbon material showing almost nochange in the layer structure even upon heat treatment at a hightemperature of 2000° C. or more. For example, non-graphitizable carbon(hard carbon), mesocarbon microbeads (MCMB) calcined at 1500° C. orless, mesophase pitch carbon fiber (MCF), and the like. A representativeexample is Carbotron® P available from Kureha Corporation.

((G) Oxide of One or More Metals Selected from Si, Sn, and Al)

Examples of (G) the oxide of one or more metals selected from Si, Sn,and Al include silicon oxides, tin oxides, and the like, which arecapable of doping/de-doping lithium ions.

Examples include SiO_(x) having a structure in which ultrafine particlesof Si are dispersed in SiO₂ and the like. When this material is used asa negative-electrode active material, charge and discharge can besmoothly performed because Si reacted with Li is of ultrafine particles.Further, when a compound (paste) for forming a negative-electrodeactive-material layer is made of this material, the coatability and theadhesiveness of a negative-electrode mixture layer with a currentcollector are also good because SiO_(x) particles themselves having theabove structure have small surface areas.

It is noted that a higher capacity and better charge-discharge cyclecharacteristics can be simultaneously obtained when SiO_(x) is usedalong with graphite as (E) the negative-electrode active material in aspecific ratio. This is because SiO_(x) shows a large volume change uponcharge and discharge.

((H) One or More Metals Selected from Si, Sn, and Al, and an AlloyComprising the One or More Metals and Further Comprising or notComprising Lithium)

Examples of (H) the one or more metals selected from Si, Sn, and Al, andan alloy comprising the one or more metals and further comprising or notcomprising lithium include metals such as silicon, tin, and aluminum;silicon alloys; tin alloys; aluminum alloys; and the like. Materials inwhich these metals and alloys are alloyed with lithium during charge anddischarge can also be used.

Preferred specific examples of these include elemental metals (forexample, powdered materials) such as, for example, silicon (Si) and tin(Sn); alloys of the above metals; compounds containing the above metals;alloys including tin (Sn) and cobalt (Co) in the above metals; and thelike as described in WO2004/100293, Japanese Unexamined PatentApplication, Publication No. 2008-016424, and the like. Use of the abovemetals for electrodes is preferred because a high charge capacity can beobtained, and expansion and contraction of the volume upon charge anddischarge are relatively small. Further, these metals are known to bealloyed with Li upon charging, leading to a high charge capacity whenthey are used for negative electrodes of lithium-ion secondarybatteries. Therefore, use of these metals is also preferred in thisregard.

Further, a negative-electrode active material formed from siliconpillars having a submicron diameter, a negative-electrode activematerial including silicon fiber, and the like as described inWO2004/042851, WO2007/083155, and the like can be used.

((I) Lithium Titanium Oxide)

Examples of (I) the lithium titanium oxide can include lithium titanateshaving the spinel structure, lithium titanates having the ramsdellitestructure, and the like.

Lithium titanates having the spinel structure can include, for example,Li_(4+α)Ti₅O₁₂ (α varies within the range of 0≤α≤3 due to charge anddischarge reactions). Further, lithium titanates having the ramsdellitestructure include, for example, Li_(2+β)Ti₃O₇ varies within the range of0≤β≤3 due to charge and discharge reactions). These negative-electrodeactive materials can be prepared in accordance with the methods ofmanufacture and the like as described in, for example in JapaneseUnexamined Patent Application, Publication No. 2007-018883, JapaneseUnexamined Patent Application, Publication No. 2009-176752, and thelike.

For example, hard carbon; oxides such as TiO₂, V₂O₃, and MoO₃; and thelike may be used as a negative-electrode active material in a sodium-ionsecondary battery where cations in a nonaqueous electrolytic solutionare mostly sodium ions. For example, the followings can be used as apositive-electrode active material in a sodium-ion secondary batterywhere cations in a nonaqueous electrolytic solution are mostly sodiumions: sodium-containing transition metal composite oxides such asNaFeO₂, NaCrO₂, NaNiO₂, NaMnO₂, and NaCoO₂; mixtures of multipletransition metals such as Fe, Cr, Ni, Mn, and Co of thosesodium-containing transition metal composite oxides; those in which someof the transition metals of these sodium-containing transition metalcomposite oxides are replaced with different metals other than thetransition metals; phosphate compounds of transition metals such asNa₂FeP₂O₇ and NaCo₃(PO₄)₂P₂O₇; sulfides such as TiS₂ and FeS₂; orelectrically conductive polymers such as polyacethylene,poly(p-phenylene), polyaniline, and polypyrrole; activated carbon;radical-generating polymers; carbon materials; and the like.

[Negative-Electrode Current Collector]

The negative electrode has a negative-electrode current collector. Asthe negative-electrode current collector, for example, copper, stainlesssteel, nickel, titanium, or alloys thereof can be used.

[Negative-Electrode Active-Material Layer]

In the negative electrode, for example, a negative-electrodeactive-material layer is formed on at least one surface of thenegative-electrode current collector. The negative-electrodeactive-material layer includes, for example, the aforementionednegative-electrode active material, a binding agent, and, if desired, anelectrically conductive agent.

Examples of the binding agent include polytetrafluoroethylene,poly(vinylidene fluoride), a styrene-butadiene rubber (SBR) resin, orthe like.

Examples of the electrically conductive agent include, for example,carbon materials such as acetylene black, Ketjen black, carbon fiber, orgraphite (granular graphite and flaky graphite).

[Method of Manufacturing Electrodes (the Positive Electrode and theNegative Electrode)]

An electrode can be obtained, for example, by dispersing and kneadingpredetermined loading amounts of an active material, a binding agent,and, if desired, an electrically conductive agent into a solvent such asN-methyl-2-pyrrolidone (NMP) and water, and applying the resulting pasteon a current collector, and drying to form an active-material layer. Theresulting electrode is preferably compressed by a method such as rollpress to adjust the electrode to a suitable density.

[(d) Separator]

The nonaqueous electrolytic solution battery according to the presentinvention includes the separator. As a separator for preventing contactbetween the positive electrode and the negative electrode, non-wovenfabrics and porous sheets made of polyolefins such as polypropylene andpolyethylene; cellulose; paper; or glass fiber; and the like. Thesefilms are preferably microporous so that penetration by an electrolyticsolution can be facilitated for easy permeation of ions.

Polyolefin separators include, for example, lithium-ion permeablemembranes capable of electrically insulating the positive electrode fromthe negative electrode, for example, microporous polymer films such asporous polyolefin films. Specific examples of porous polyolefin filmsinclude, for example, porous polyethylene films alone, or multilayerfilms in which a porous polyethylene film and a porous polypropylenefilm are layered. Examples also include composite films with a porouspolyethylene film and a polypropylene film, and the like.

[Housing]

As a housing for nonaqueous electrolytic solution batteries which can beused when assembling the present nonaqueous electrolytic solutionbattery, for example, metal cans of a coin-type, a cylinder-type, arectangle-type, and the like; and laminate housings can be used.Materials for metal cans include, for example, nickel-plated steelsheets, stainless steel sheets, nickel-plated stainless steel sheets,aluminum or an alloy thereof, nickel, titanium, and the like. Aslaminate housings, for example, laminate films such as an aluminumlaminate film, a stainless steel laminate film, laminate films ofsilica-coated polypropylene and polyethylene can be used.

There is no particular limitation for the configuration of thenonaqueous electrolytic solution battery according to the presentembodiment, but the configuration may be such that an electrode elementhaving a positive electrode and a negative electrode arranged in acountering manner, and a nonaqueous electrolytic solution are includedinside a housing. There is no particular limitation for the shape of thenonaqueous electrolytic solution battery, but a coin-like, cylindrical,rectangular, or aluminum laminate sheet-like electrochemical device maybe assembled with the components described above.

EXAMPLES

Below, the present invention will be described in more detail withreference to Examples, but the present invention shall not be limited tothese in any sense. It is noted that Examples with sub-numbers may becollectively denoted, for example, Examples 1-1 to 1-41 may becollectively referred to as Example 1. The same may apply to Example 2and so on and Comparative Examples, and electrolytic solution Nos.

Below, the methods of synthesizing difluoro ionic complexes (cis/transisomers) and tetrafluoro ionic complexes will be described. The methodsdisclosed in Patent Document 6, Nonpatent Document 1, and PatentDocument 5 were used herein to synthesize ionic complexes. However,methods other than these may be used to synthesize them.

In any cases, raw materials and products were handled under a nitrogenatmosphere of a dew point of −50° C. or less. Further, a glass reactorused was dried at 150° C. for 12 hours or more, and then cooled to roomtemperature under a nitrogen stream of a dew point of −50° C. or lessbefore use.

[Synthesis Example 1] Synthesis of (1a-Cis) and (1a-Trans)

Lithium tris(oxalato)phosphate as a three-coordinate complex of oxalicacid was obtained according to the method disclosed in Patent Document5. Lithium tris(oxalato)phosphate (30 g, 99.4 mmol) was dissolved indimethyl carbonate (hereinafter, referred to as DMC) (120 mL), andhydrogen fluoride (hereinafter, referred to as HF) (11.9 g, 596.4 mmol)was then added. After stirring at 25° C. for 48 hours, residual HF andDMC were removed under reduced pressure. Then, DMC (60 mL) was added,and the concentrated residue was dissolved as much as possible, and thenconcentrated until the concentration of an Li salt became about 45 mass%. After removing insoluble components including oxalic acid byfiltration, 49 g of a DMC solution of a mixture of (1a-Cis) and(1a-Trans) was obtained. Dichloromethane (hereinafter, referred to as“CH₂Cl₂”) was added to the DMC solution of the mixture at roomtemperature, and stirred for 12 hours to obtain a precipitated solid.The solid was separated from the mother liquor by filtration, and themother liquor was distilled to remove DMC under reduced pressure until asolid was obtained. The filtered solid and the solid obtained from themother liquor were separately dissolved in CH₂Cl₂ to separately prepareDMC solutions with a concentration of about 45 mass %, and CH₂Cl₂ wasthen added to allow a solid to precipitate. The solids were recoveredseparately by filtration, and the preparation of a DMC solution with aconcentration of about 45 mass % and the precipitation of a solid werefurther repeated for several times by a similar procedure to obtain(1a-Cis) and (1a-Trans) with F and P purities of 99.9 mol % (asdetermined by NMR).

(1a-Cis) and (1a-Trans) were dissolved separately in acetonitrile, andsubjected to LC/MS (the ESI method, polarity: negative, fragmentvoltage: 50 V) to measure molecular weight. A parent ion was observed atm/z 244.9 for both, which is consistent with a theoretical mass numberof 244.93 (the anion moiety). Further, the steric conformation wasdetermined by the single crystal X-ray structure analysis. FIG. 1 showsthe analysis result of (1a-Cis). It has been confirmed that (1a-Cis) isin the cis configuration in which two fluorine atoms are bonded in thesame side when viewed from the central element.

(1a-Cis) and (1a-Trans) clearly have the same atomic composition butdifferent structures because they have the same mass, and F-NMR andP-NMR show their peaks at different positions. Further, (1a-Trans) wasdetermined to be in the trans configuration in which two fluorine atomsare bonded in the opposite sides when viewed from the central element asdetermined by the single crystal X-ray structure analysis.

[Synthesis Example 2] Synthesis of (5a-Tetra)

Reactions were performed according to the method described in PatentDocument 6. To a 500 mL glass flask, added were 20.0 g (132 mmol) ofLiPF₆, 110 mL of dimethyl carbonate (DMC), and 11.9 g (132 mmol) ofoxalic acid. At this point, LiPF₆ was completely dissolved, but themajority of oxalic acid remained unresolved. With stirring at 25° C.,13.4 g (79 mmol) of SiCl₄ was added dropwise to the flask, and stirringwas then continued for 4 hours. Subsequently, tetrafluorosilane andhydrochloric acid were removed under reduced pressure to obtain a crudeDMC solution containing the ionic complex (5a-Tetra) as the maincomponent (a purity of 91 mol %). This solution was concentrated untilthe concentration of an Li salt became about 50 mass % to obtain 51 g ofa concentrated liquid. After removing insoluble components byfiltration, CH₂Cl₂ was added with stirring at room temperature. Afterstirring for 12 hours, a precipitated solid was recovered by filtration.Again, it was dissolved in DMC to prepare a DMC solution with anconcentration of an Li-salt of about 50 mass %, and then the addition ofCH₂Cl₂, precipitation of a solid, and recovery of a solid were performedby a similar procedure to obtain (5a-Tetra) with F and P purities of99.9%. [Synthesis Example 3] Synthesis of (1b-Cis) and (1b-Trans)(1b-Cis) and (1b-Trans) were each obtained as in Synthesis Example 1except that hexafluoro-2-hydroxyisobutyric acid was used as a rawmaterial instead of oxalic acid.

[Synthesis Example 3] Synthesis of (6a-Cis) and (6a-Trans) as Na Adductsof (1a-Cis) and (1a-Trans)

A Dow Chemical strongly acidic cation exchange resin 252 (hereinafter,referred to as the ion exchange resin) was weighed out to give 500 g,and immersed in 0.1 N aqueous sodium hydroxide (2.5 kg), and stirred at25° C. for 6 hours. The ion exchange resin was collected by filtration,and washed thoroughly with pure water until the pH of a wash liquidbecame 8 or less. Then, water was removed by drying under reducedpressure for 12 hours (120° C., 1.3 kPa). The (1a-Cis)/EMC solution witha concentration of 10 mass % was prepared, to which the dried ionexchange resin in a weight corresponding to half of the weight of theliquid was added, and stirred at 25° C. for 6 hours. Then, the ionexchange resin was removed by filtration to obtain a (6a-Cis)/EMCsolution (with a concentration of about 10 mass %) in which cations ofLi⁺ had been exchanged with Na⁺. The ratio of Na⁺/Li⁺ was 99.5 whencations were quantified by ion chromatography. Further, the(6a-Trans)/EMC solution with a concentration of about 10 mass % wasobtained as in the method described above except that the (1a-Trans)/EMCsolution with the same concentration was substituted for the(1a-Cis)/EMC solution.

[Synthesis Example 5] Synthesis of (5b-Tetra) as an Na Adduct of(5a-Tetra)

A (5b-Tetra)/EMC solution with a concentration of about 10 mass % inwhich cations of Li⁺ had been exchanged with Na⁺ was obtained bysubstituting a (5a-Tetra)/EMC solution for the (1a-cis)/EMC solutionused in Synthesis Example 4. The ratio of Na⁺/Li⁺ was 99.4 when cationswere quantified by ion chromatography.

[Synthesis Example 6] Synthesis of (6b-Cis) and (6b-Trans) as K Adductsof (1a-Cis) and (1a-Trans)

(6b-Cis)/EMC and (6 b-Trans)/EMC solutions with a concentration of about10 mass % in which cations of Li⁺ had been exchanged with K⁺ wereobtained by substituting 0.1 N aqueous potassium hydroxide (2.5 kg) for0.1 N aqueous sodium hydroxide (2.5 kg) used in Synthesis Example 4. Theratio of K⁺/L^(i)+ was 99.6 for both solutions when cations werequantified by ion chromatography.

[Synthesis Example 7] Synthesis of (6c-Cis) and (6c-Trans) as TMPAAdducts of (1a-Cis) and (1a-Trans)

To 90 g of EMC, 5.7 g (41.7 mmol) of trimethylpropylammonium chlorideand 10.0 g (39.7 mmol) of (1a-Cis) were added, and stirred at 45° C. for6 hours. After cooled to 5° C., insoluble materials were removed byfiltration to obtain a (6c-Cis)/EMC solution (with a concentration ofabout 13 mass %) in which cations of Li⁺ had been exchanged withtrimethylpropylammonium cations (hereinafter, referred to as TMPA).Further, the (6c-Trans)/EMC solution with a concentration of about 13mass % was obtained as in the method described above except that(1a-Trans) in the same weight was substituted for (1a-Cis). The ratio ofTMPA/Li⁺ was 98.5 for both solutions when cations were quantified by ionchromatography.

[Synthesis Example 8] Synthesis of (6d-Cis) and (6d-Trans) as PP13Adducts of (1a-Cis) and (1a-Trans)

To 90 g of EMC, 7.4 g (41.7 mmol) of 1-butyl-1-methylpyrrolidiniumchloride and 10.0 g (39.7 mmol) of (1a-Cis) were added, and stirred at45° C. for 6 hours. After cooled to 5° C., insoluble materials wereremoved by filtration to obtain a (6d-Cis)/EMC solution (with aconcentration of about 15 mass %) in which cations of Li⁺ had beenexchanged with 1-butyl-1-methylpyrrolidinium cations (hereinafter,referred to as PP13). Further, the (6d-Trans)/EMC solution with aconcentration of about 15 mass % was obtained as in the method describedabove except that (1a-Trans) in the same weight was substituted for(1a-Cis). The ratio of PP13/Li⁺ was 98.3 for both solutions when cationswere quantified by ion chromatography.

[Synthesis Example 9] Synthesis of (1c-Cis) and (1c-Trans)

(1c-Cis), which is (1-Cis) where the anion moiety is (1c) and A=Li, and(1c-Trans), which is (1-Trans) where the anion moiety is (Trans-c) andA=Li, were each obtained by applying the method described in Non-PatentDocument 1.

[Preparation of Nonaqueous Electrolytic Solutions Nos. 1-1 to 1-41 andComparative Electrolytic Solutions Nos. 1-1 to 1-6]

In a dry box under a nitrogen atmosphere of a dew point of −50° C. orless, LiPF₆ as an electrolyte was dissolved and prepared in a preheatedand dissolved nonaqueous solvent of ethylene carbonate (EC) andethylmethyl carbonate (EMC) (volume ratio 1:2) so that the concentrationof LiPF₆ was 1 mol/liter, and then various ionic complex/EMC solutionsaccording to the present invention and the group (II) compounds asdescribed above were added in a predetermined amount to prepare thenonaqueous electrolytic solutions Nos. 1-1 to 1-41 according to thepresent invention and the comparative electrolytic solutions Nos. 1-1 to1-6 shown in Table 1 below.

TABLE 1 Trans Tetrafluoro isomer/ complex/ Group (I) Group (III) CisGroup (IV) Cis compound Content Content compound Content isomer compoundContent isomer (Cis (mass Group (II) (mass Trans (mass (mass Tetrafluoro(mass (mass Electrolytic solution No, isomer) %) compound %) isomer %)ratio) complex %) ratio) Electrolytic solution No. 1-1 (1a-Cis)  0.05(II-1-5) 3.0 — — — — — — Electrolytic solution No. 1-2 0.1 3.0 — — — — —— Electrolytic solution No. 1-3 0.8 3.0 — — — — — — Electrolyticsolution No. 1-4 1.0 3.0 — — — — — — Electrolytic solution No. 1-5 3.03.0 — — — — — — Electrolytic solution No. 1-6 5.0 3.0 — — — — — —Electrolytic solution No. 1-7 (1a-Cis) 1.0 (II-1-5) 0.5 — — — — — —Electrolytic solution No. 1-8 1.0 1.5 — — — — — — Electrolytic solutionNo. 1-9 1.0 6.0 — — — — — — Electrolytic solution No. 1-10 1.0 10.0 — —— — — — Electrolytic solution No. 1-11 1.0 15.0 — — — — — — Electrolyticsolution No. 1-12 (1a-Cis) 1.0 (II-1-5) 3.0 (1a-Trans) 0.002 0.002 — — —Electrolytic solution No. 1-13 1.0 3.0 0.004 0.004 — — — Electrolyticsolution No. 1-14 1.0 3.0 0.01 0.01 — — — Electrolytic solution No. 1-15(1a-Cis) 1.0 (II-1-5) 3.0 — — (5a-Tetra) 0.07 0.07 Electrolytic solutionNo. 1-16 1.0 3.0 — — 0.14 0.14 Electrolytic solution No. 1-17 1.0 3.0 —— 0.20 0.20 Electrolytic solution No. 1-18 (1a-Cis) 0.5 (II-1-5) 1.5(1a-Trans) 0.001 0.002 (5a-Tetra) 0.035 0.07 Electrolytic solution No.1-19 0.5 3.0 0.0025 0.005 0.06 0.12 Electrolytic solution No. 1-20 1.01.5 0.002 0.002 0.07 0.07 Electrolytic solution No. 1-21 1.0 3.0 0.0040.004 0.14 0.14 Electrolytic solution No. 1-22 1.0 6.0 0.01 0.01 0.200.20 Electrolytic solution No. 1-23 3.0 3.0 0.015 0.005 0.36 0.12Electrolytic solution No. 1-24 3.0 6.0 0.03 0.01 0.60 0.20 Electrolyticsolution No. 1-25 (1a-Cis) 0.5 (II-1-5) 3.0 (1a-Trans) 0.004 0.004(5a-Tetra) 0.14 0.14 (1b-Cis) 0.5 Electrolytic solution No. 1-26(1a-Cis) 1.0 (II-1-5) 1.5 (1a-Trans) 0.004 0.004 (5a-Tetra) 0.14 0.14(II-1-6) 1.5 Electrolytic solution No. 1-27 (1a-Cis) 1.0 (II-1-5) 3.0(1a-Trans) 0.002 0.002 (5a-Tetra) 0.14 0.14 (1b-Trans) 0.002 0.002Electrolytic solution No. 1-28 (1a-Cis) 1.0 (II-1-5) 3.0 (1a-Trans)0.004 0.004 (5a-Tetra) 0.07 0.07 (5b-Tetra) 0.07 0.07 Electrolyticsolution No. 1-29 (1b-Cis) 1.0 (II-1-5) 3.0 (1a-Trans) 0.004 0.004(5a-Tetra) 0.14 0.14 Electrolytic solution No. 1-30 (1a-Cis) 1.0 3.0(1b-Trans) 0.004 0.004 (5a-Tetra) 0.14 0.14 Electrolytic solution No.1-31 (1a-Cis) 1.0 3.0 (1a-Trans) 0.004 0.004 (5b-Tetra) 0.14 0.14Electrolytic solution No. 1-32 (6a-Cis) 1.0 (II-1-5) 3.0 (1a-Trans)0.004 0.004 (5a-Tetra) 0.14 0.14 Electrolytic solution No. 1-33 (6b-Cis)1.0 3.0 0.004 0.004 0.14 0.14 Electrolytic solution No. 1-34 (6c-Cis)1.0 3.0 0.004 0.004 0.14 0.14 Electrolytic solution No. 1-35 (6d-Cis)1.0 3.0 0.004 0.004 0.14 0.14 Electrolytic solution No. 1-36 (1c-Cis)0.8 3.0 0.004 0.004 0.14 0.14 Electrolytic solution No. 1-37 (1a-Cis)1.0 (II-1-5) 3.0 (6a-Trans) 0.004 0.004 (5a-Tetra) 0.14 0.14Electrolytic solution No. 1-38 1.0 3.0 (6b-Trans) 0.004 0.004 0.14 0.14Electrolytic solution No. 1-39 1.0 3.0 (6c-Trans) 0.004 0.004 0.14 0.14Electrolytic solution No. 1-40 1.0 3.0 (6d-Trans) 0.004 0.004 0.14 0.14Electrolytic solution No. 1-41 1.0 3.0 (1c-Trans) 0.004 0.004 0.14 0.14Comparative electrolytic — — — — — — — — — — solution No. 1-1Comparative electrolytic (1a-Cis) 1.0 — — — — — — — — solution No. 1-2Comparative electrolytic (1a-Cis) 0.5 — — — — — — — — solution No. 1-3(1b-Cis) 0.5 Comparative electrolytic — — (II-1-5) 3.0 — — — — — —solution No. 1-4 Comparative electrolytic — — (II-1-5) 3.0 (1a-Trans)1.0 — — — — solution No. 1-5 Comparative electrolytic — — (II-1-5) 3.0(1a-Trans) 1.0 — (5a-Tetra) 0.14 — solution No. 1-6<Production of NMC Positive Electrode>

A LiNi_(1/3)Mn_(1/3)O_(1/3)O₂ (NMC) powder as a positive-electrodeactive material was dry-mixed with acetylene black (electricallyconductive agent), and then uniformly dispersed and mixed into theN-methyl-2-pyrrolidone (NMP) in which poly(vinylidene fluoride) (PVDF)was pre-dissolved, and NMP for adjusting the viscosity was further addedto prepare an NMC mixture paste. The resulting paste was applied to analuminum foil (current collector), dried, and pressurized. Then thealuminum foil was processed into a predetermined size to obtain a testNMC positive electrode. The ratio of solid contents in the positiveelectrode was NMC:electrically conductive agent:PVDF=85:5:10 (by themass ratio).

<Production of Graphite Negative Electrode>

A graphite powder as a negative-electrode active material was uniformlydispersed and mixed into NMP in which PVDF as a binding agent waspre-dissolved, and NMP for adjusting the viscosity was further added toprepare a graphite mixture paste. The above paste was applied to acopper foil (current collector), dried, and pressurized. Then the copperfoil was processed into a predetermined size to obtain a test graphitenegative electrode. The ratio of solid contents in the negativeelectrode was graphite powder:PVDF=90:10 (by the mass ratio).

<Production of Nonaqueous Electrolytic Solution Batteries>

Aluminum laminate housing cells (with a capacity of 30 mAh) includingthe above test NMC positive electrode, the above test graphite negativeelectrode, and a cellulose separator were respectively impregnated withone of the nonaqueous electrolytic solutions Nos. 1-1 to 1-41 and thecomparative electrolytic solutions Nos. 1-1 to 1-6 to obtain thenonaqueous electrolytic solution batteries according to Examples 1-1 to1-41 and Comparative Examples 1-1 to 1-6.

Example 1, Comparative Example 1: Evaluation of Test Cells

<Evaluation 1> Low-Temperature Property (0° C.) after 500 Cycles at 60°C.

Each of the nonaqueous electrolytic solution batteries according toExamples 1-1 to 1-41 and Comparative Examples 1-1 to 1-6 was evaluatedas described below. It is noted that “-” in tables means that themeasurement is not yet performed.

First, the resulting cells were subjected to conditioning at anenvironmental temperature of 25° C. under the following conditions. Thatis, as the initial charge/discharge, constant-current andconstant-voltage charge was performed at a 0.1 C rate (3 mA) to a chargeupper limit voltage of 4.3 V, and then discharge was performed at aconstant current of a 0.2 C rate (6 mA) to a discharge cutoff voltage of3.0 V. Subsequently, a charge-discharge cycle was repeated 3 times asdescribed below: constant-current and constant-voltage charge wasperformed at a 0.2 C rate (6 mA) to a charge upper limit voltage of 4.3V, and then discharge was performed at a constant current of a 0.2 Crate (6 mA) to a discharge cutoff voltage of 3.0 V.

After this conditioning, charge and discharge tests were performed at anenvironmental temperature of 60° C. The following charge-discharge cyclewas repeated for 500 times: constant-current and constant-voltage chargewas performed at a 3 C rate (90 mA) to a charge upper limit voltage of4.3 V, and discharge was performed at a constant current of a 3 C rate(90 mA) to a discharge cutoff voltage of 3.0 V.

Next, the nonaqueous electrolytic solution batteries were cooled to 25°C., and again discharged to 3.0 V. Then constant-current andconstant-voltage charge was performed to 4.3 V at a 0.2 C rate at 0° C.Further, discharge was performed at a constant current of a 5 C rate(150 mA) to a discharge cutoff voltage of 3.0 V while maintaining thetemperature at 0° C., and the capacity obtained at that time was takenas the low-temperature property (0° C.) after prolonged cycles at 60° C.

<Evaluation 2>5C-Rate Characteristics after 500 Cycles at 60° C.

After performing 500 cycles at an environmental temperature of 60° C. inEvaluation 1 as described above, the nonaqueous electrolytic solutionbatteries were cooled to 25° C., and then again discharged to 3.0 V.Then constant-current and constant-voltage charge was performed to 4.3 Vat a 5 C rate at 25° C. Further, discharge was performed at a constantcurrent of a 5 C rate (150 mA) to a discharge cutoff voltage of 3.0 Vwhile maintaining the temperature at 25° C., and the capacity obtainedat that time was taken as the 5C-rate characteristic (25° C.) afterprolonged cycles at 60° C.

<Evaluation 3> Low-Temperature Property (0° C.) after Stored at 60° C.

Each of the nonaqueous electrolytic solution batteries according toExamples 1-1 to 1-41 and Comparative Examples 1-1 to 1-6 was subjectedto storage tests (stored for 10 days after charged to 4.3 V) at anenvironmental temperature of 60° C.

Next, the nonaqueous electrolytic solution batteries were cooled to 25°C., and again discharged to 3.0 V. Then constant-current andconstant-voltage charge was performed to 4.3 V at a 0.2 C rate at 0° C.Further, discharge was performed at a constant current of a 5 C rate(150 mA) to a discharge cutoff voltage of 3.0 V while maintaining thetemperature at 0° C., and the capacity obtained at that time was takenas the low-temperature property (0° C.) after stored at 60° C.

Evaluations 1 to 3 according to Examples 1-1 to 1-41 and ComparativeExamples 1-2 to 1-6 are shown in Table 2 as relative values when theevaluation results according to Comparative Example 1-1 are taken as100.

<Evaluation 4> Evaluation of Expansion During Charge

Using the produced cells, battery thickness was measured when charge wasperformed at an environmental temperature of 25° C. at 90 mA to 4.3 Vfor 3 hours, and storage was then performed at 90° C. for 4 hours.Change in the battery thickness between before and after the charge wasevaluated as an expansion rate (%). The expansion rate is calculatedusing the battery thickness before the charge as a denominator and ((thebattery thickness after the charge)−(the battery thickness before thecharge)) as a numerator.

<Evaluation 5> Temperature Rise Value During Overcharging Test

Overcharging tests were performed by performing charge at a constantcurrent of a 2 C rate (60 mA) continuously from a fully charged statewhere charge was performed to a charge upper limit voltage using cellssubjected to the same conditioning as Evaluation 1, under ordinarytemperature (20° C.) and under the same conditions as thecharge-discharge cycle in the conditioning. At that time, a currentcutoff time was set to 25 minutes, and the maximum surface temperatureof the battery was measured after the current cutoff, thereby definingthe difference between the measured temperature and the temperaturebefore the measurement as a temperature rise value. It is noted that themeasurement was stopped because of a possibility of ignition in the casewhere the temperature rise value was 99.9 K or more.

<Evaluation 6> Evaluation of Combustibility

Combustibility of an electrolytic solution was evaluated by measuringthe extent of combustion of the flame ignited with a test flame.Specifically, the evaluation was performed using a test piece preparedby impregnating a glass fiber filter cut out to the size of 150 mm×12 mmwith 1.0 ml of the electrolytic solution. The criteria for evaluatingnon-combustibility, flame retardancy, self-extinguishment, andcombustibility are shown below.

(a) Non-combustibility: A case where ignition did not occur at all evenif a test flame was contacted was judged as non-combustible.

(b) Flame retardancy: A case where the ignited flame did not reach the25-mm line was judged as flame-retardant.

(c) Self-extinguishment: A case where the ignited flame was extinguishedbetween the 25- and 100-mm lines was judged as self-extinguishing.

(d) Combustibility: A case where the ignited flame went over the 100-mmline was judged as combustible.

TABLE 2 (Positive electrode; NMC Negative electrode; Graphite)Low-temperature 5C-rate Low-temperature property characteristic propertyTemperature (0° C.) (25° C.) (0° C.) Expansion rise after prolongedafter prolonged after stored rate value Combustibility Electrolyticsolution No, cycles at 60° C. cycles at 60° C. at 60° C. (%) (K) testExample 1-1 Electrolytic solution No. 1-1 131.1 133.3 117.9 7.5 — Self-extinguishing Example 1-2 Electrolytic solution No. 1-2 131.7 133.5118.4 6.7 — Self- extinguishing Example 1-3 Electrolytic solution No.1-3 131.9 133.7 119.1 5.8 — Self- extinguishing Example 1-4 Electrolyticsolution No. 1-4 132.3 134.5 119.6 5.8 — Self- extinguishing Example 1-5Electrolytic solution No. 1-5 132.1 134.0 118.8 6.7 — Self-extinguishing Example 1-6 Electrolytic solution No. 1-6 131.3 133.0117.8 6.7 — Self- extinguishing Example 1-7 Electrolytic solution No.1-7 131.5 133.2 118.1 9.2 — Combustible Example 1-8 Electrolyticsolution No. 1-8 131.8 134.1 118.2 8.3 — Self- extinguishing Example 1-9Electrolytic solution No. 1-9 132.0 133.9 118.8 5.0 — Flame- retardantExample 1-10 Electrolytic solution No. 1-10 131.6 133.6 117.6 4.2 — Non-combustible Example 1-11 Electrolytic solution No. 1-11 130.1 131.2116.0 3.3 — Non- combustible Example 1-12 Electrolytic solution No. 1-12132.4 135.0 119.9 5.8 — — Example 1-13 Electrolytic solution No. 1-13133.0 135.5 120.1 5.8 — — Example 1-14 Electrolytic solution No. 1-14133.9 134.9 120.2 5.0 — — Example 1-15 Electrolytic solution No. 1-15132.6 134.6 120.0 5.8 — — Example 1-16 Electrolytic solution No. 1-16133.1 135.1 120.3 6.7 — — Example 1-17 Electrolytic solution No. 1-17133.4 134.9 120.5 6.7 — — Example 1-18 Electrolytic solution No. 1-18131.2 133.6 118.9 8.3 — — Example 1-19 Electrolytic solution No. 1-19131.9 133.8 119.4 7.5 — — Example 1-20 Electrolytic solution No. 1-20132.2 134.0 119.7 7.5 — — Example 1-21 Electrolytic solution No. 1-21134.0 135.9 120.5 5.8 — — Example 1-22 Electrolytic solution No. 1-22132.2 134.5 119.9 5.0 — — Example 1-23 Electrolytic solution No. 1-23132.1 134.1 119.4 5.8 — — Example 1-24 Electrolytic solution No. 1-24131.4 133.4 118.3 5.0 — — Example 1-25 Electrolytic solution No. 1-25133.6 135.8 120.2 5.8 — — Example 1-26 Electrolytic solution No. 1-26133.0 135.7 120.4 5.8 — — Example 1-27 Electrolytic solution No. 1-27133.8 136.1 120.5 5.8 — — Example 1-28 Electrolytic solution No. 1-28133.2 136.0 119.9 5.8 — — Example 1-29 Electrolytic solution No. 1-29133.1 135.5 119.8 5.8 — — Example 1-30 Electrolytic solution No. 1-30133.1 135.7 120.1 5.8 — — Example 1-31 Electrolytic solution No. 1-31133.7 135.6 119.4 5.8 — — Example 1-32 Electrolytic solution No. 1-32133.6 135.2 119.7 5.8 — — Example 1-33 Electrolytic solution No. 1-33132.9 135.4 119.5 5.8 — — Example 1-34 Electrolytic solution No. 1-34132.8 134.7 119.3 5.8 — — Example 1-35 Electrolytic solution No. 1-35132.8 134.8 118.6 5.8 — — Example 1-36 Electrolytic solution No. 1-36132.9 135.4 119.7 5.8 — — Example 1-37 Electrolytic solution No. 1-37132.9 135.4 119.5 5.8 — — Example 1-38 Electrolytic solution No. 1-38132.8 135.3 119.0 5.8 — — Example 1-39 Electrolytic solution No. 1-39132.6 134.2 118.7 5.8 — — Example 1-40 Electrolytic solution No. 1-40132.5 134.5 118.5 5.8 — — Example 1-41 Electrolytic solution No. 1-41132.7 135.1 119.2 5.8 — — Comparative Comparative electrolytic 100.0100.0 100.0 13.3 >99.9 Combustible Example 1-1 solution No. 1-1Comparative Comparative electrolytic 126.6 132.6 111.2 11.7 — — Example1-2 solution No. 1-2 Comparative Comparative electrolytic 126.3 131.9110.8 11.7 — — Example 1-3 solution No. 1-3 Comparative Comparativeelectrolytic 103.0 100.5 104.3 8.3 — — Example 1-4 solution No. 1-4Comparative Comparative electrolytic 128.0 131.8 114.0 6.7 — — Example1-5 solution No. 1-5 Comparative Comparative electrolytic 128.7 132.4114.2 7.5 — — Example 1-6 solution No. 1-6(Regarding Examples 1-1 to 1-11)

As seen from the results in Tables 1 and 2, the nonaqueous electrolyticsolution batteries including the difluoro ionic complex (1a-Cis) in thecis configuration from Synthesis Example 1 according to Example and thecyclic phosphazene compound (II-1-5) showed a higher discharge capacity(0° C.) after prolonged cycles at 60° C. and a higher 5C-ratecharacteristic after prolonged cycles at 60° C. as compared with thenonaqueous electrolytic solution battery including neither (1a-Cis) nor(II-1-5) (Comparative Example 1-1).

Comparison of Example 1-4 with Comparative Example 1-2 revealed that thenonaqueous electrolytic solution battery including both (1a-Cis) and(II-1-5) showed higher effects than the nonaqueous electrolytic solutionbattery including (1a-Cis) only.

This can be explained as follows. When the nonaqueous electrolyticsolution according to the present invention includes the difluoro ioniccomplex (1a-Cis) and the cyclic phosphazene compound (II-1-5), theseadditives are reductively decomposed on a negative electrode in theorder of the difluoro ionic complex (1a-Cis) and then the cyclicphosphazene compound (II-1-5) during charge at the first cycle to form astable film (SEI) on the surface of the negative electrode. That is, theabove reaction film layer having a high ion conductivity and the SEIhaving long-term stability and covering the surface of the negativeelectrode can prevent side reactions such as decomposition of a solventwhich otherwise occur on the surface of the negative electrode. This, inturn, can reduce the initial irreversible capacity of the nonaqueouselectrolytic solution battery, and also improve long-term durability andoutput characteristics.

These appear to reflect significantly improved properties such as thedischarge capacity (0° C.) after prolonged cycles at 60° C. and the5C-rate characteristic (25° C.) as shown in Table 2, which supports thatthe present novel combination of the difluoro ionic complex (1a-Cis) anda cyclic phosphazene compound such as (II-1-5) can provide unprecedentedeffects for improving performance.

Comparisons of Examples 1-1 to 1-6 revealed that the effects of thedifluoro ionic complex (1a-Cis) were able to be slightly observed evenwhen the content was 0.05 mass %, and were increased as the content ofthe ionic complex increased from 0.05 mass % to 0.1, 0.8, and 1.0 mass%. On the other hand, when the content of the difluoro ionic complex(1a-Cis) was 3.0 mass % (Example 1-5), the effects were slightlydecreased as compared with the case where the content was 1.0 mass %(Example 1-4). In the case of 5.0 mass % (Example 1-6), the effects weresignificantly decreased as compared with the case of 1.0 mass %. Thismay be assumed as follows. The viscosity of a nonaqueous electrolyticsolution is increased when the content of the difluoro ionic complex(1a-Cis) reaches 3 mass % or more. This may restrict movement of cationswithin a nonaqueous electrolytic solution battery, resulting indecreased battery performance.

Comparisons of Examples 1-4 and 1-7 to 1-11 revealed that the effects ofthe cyclic phosphazene compound (II-1-5) were able to be slightlyobserved even when the content was 0.5 mass %, and were increased as thecontent of (II-1-5) increased from 0.5 mass % to 1.5 and 3.0 mass %. Onthe other hand, when the content of the (II-1-5) was 6.0 mass % (Example1-9), the effects were slightly decreased as compared with the casewhere the content was 3.0 mass % (Example 1-4). In the case of 10 or 15mass % (Example 1-10 or 1-11), the effects were decreased as comparedwith the case of 3.0 mass %.

Further, comparison of Example 1-4 with Comparative Example 1-5 revealedthat the nonaqueous electrolytic solution battery from Example 1-4including the difluoro ionic complex (1a-Cis) in the cis configurationand the cyclic phosphazene compound (II-1-5) improved not only thedischarge capacity (0° C.) after prolonged cycles at 60° C. but also thedischarge capacity (0° C.) after stored at 60° C. as compared with thenonaqueous electrolytic solution battery from Comparative Example 1-5including the difluoro ionic complex (1a-Trans) in the transconfiguration and the cyclic phosphazene compound (II-1-5). This isinferred to be a result that the different rates of the reductivedecomposition reaction between (1a-Cis) in the cis configuration and(1a-Trans) in the trans configuration may alter the selectivity of thereductive decomposition reaction (the presence or absence of solventdecomposition), resulting in different main components in SEIs formedtherefrom, which is likely responsible for the difference in the effectsof SEIs for improving the battery performance in the end.

(Regarding Examples 1-12 to 1-14)

Examples 1-12 to 1-14 where nonaqueous electrolytic solutions contain 3types of compounds: the difluoro ionic complex (1a-Cis) in the cisconfiguration, the difluoro ionic complex (1a-Trans) in the transconfiguration according to Synthesis Example 1, and the cyclicphosphazene compound (II-1-5) were found to have a tendency for furtherincreasing the discharge capacity (0° C.) after stored at 60° C. withoutdecreasing the discharge capacity (0° C.) after prolonged cycles at 60°C. as compared with the nonaqueous electrolytic solution battery(Example 1-4) including the above (1a-Cis) and (II-1-5).

Further, as the ratio of the difluoro ionic complex (1a-Trans) in thetrans configuration to the difluoro ionic complex (1a-Cis) in the cisconfiguration, i.e., difluoro ionic complex (1-Trans)/difluoro ioniccomplex (1-Cis) (by the mass ratio) increased from 0.002 to 0.004 and0.01, the discharge capacity (0° C.) after stored at 60° C. was found toshow a moderate improving tendency without impairing the dischargecapacity (0° C.) after prolonged cycles at 60° C.

(Regarding Examples 1-15 to 1-17)

Moreover, Examples 1-15 to 1-17 where the nonaqueous electrolyticsolutions contain 3 types of compounds: the difluoro ionic complex(1a-Cis), cyclic phosphazene compound (II-1-5), and the tetrafluoroionic complex (5a-Tetra) were found to have a tendency for furtherimproving the discharge capacity (0° C.) after stored at 60° C. withoutdecreasing the discharge capacity (0° C.) after prolonged cycles at 60°C. and the 5C-rate characteristic (25° C.) as compared with thenonaqueous electrolytic solution battery (Example 1-4) including(1a-Cis) and the cyclic phosphazene compound (II-1-5).

Further, comparison of Example 1-16 with Comparative Example 1-6revealed that the nonaqueous electrolytic solution battery including 3types of compounds: (1a-Cis), (II-1-5), and (5a-Tetra) showed highereffects as compared with the nonaqueous electrolytic solution batteryincluding (1a-Trans), (II-1-5), and (5a-Tetra).

Further, as the ratio of the tetrafluoro ionic complex (5a-Tetra) to thedifluoro ionic complex (1a-Cis) in the cis configuration, i.e.,tetrafluoro ionic complex (5a-Tetra)/difluoro ionic complex (1-Cis) (bythe mass ratio) increased from 0.07 to 0.14 and 0.20, the dischargecapacity (0° C.) after stored at 60° C. was found to show an improvingtendency without impairing the discharge capacity (0° C.) afterprolonged cycles at 60° C.

(Regarding Examples 1-18 to 1-24)

Further, as shown in Examples 1-18 to 1-24, the nonaqueous electrolyticsolutions containing a compound(s) selected from the four groups of thedifluoro ionic complex (1a-Cis) in the cis configuration from SynthesisExample 1, the cyclic phosphazene compound (II-1-5), the difluoro ioniccomplex (1a-Trans) in the trans configuration from Synthesis Example 1,and the tetrafluoro ionic complex (5a-Tetra) from Synthesis Example 2were found to have a tendency for improving the discharge capacity (0°C.) after prolonged cycles at 60° C., the 5C-rate characteristic (25°C.), and the discharge capacity (0° C.) after stored at 60° C. ascompared with the nonaqueous electrolytic solutions which did notcontain the tetrafluoro ionic complex (5a-Tetra) (Examples 1-12 to 1-14)and the nonaqueous electrolytic solutions which did not contain thedifluoro ionic complex (1a-Trans) in the trans configuration (Examples1-15 to 1-17) (For example, from comparisons of Examples 1-13 and 1-16with Example 1-21 where the contents of the group (I) compound and thegroup (II) compound were similar between the corresponding Examples).

(Regarding Examples 1-25 to 1-31)

Similarly to the above, the low-temperature property (0° C.) afterprolonged cycles at 60° C., the 5C-rate characteristic (25° C.) afterprolonged cycles at 60° C., and the low-temperature property (0° C.)after stored at 60° C. were shown to be excellent also in Examples 1-25to 1-31, which used the difluoro ionic complex (1b-Cis) in the cisconfiguration from Synthesis Example 3 as the group (I) compound,combined and used the cyclic phosphazene compound (II-1-6) as the group(II) compound, used the difluoro ionic complex (1b-Trans) in the transconfiguration from Synthesis Example 3 as the group (III) compound,and/or used the tetrafluoro ionic complex (5b-Tetra) from SynthesisExample 5 as the group (IV) compound.

(Regarding Examples 1-32 to 1-41)

In contrast, as shown in Examples 1-21, 32, and 33, comparisons of theionic complexes (1a-Cis), (6a-Cis), and (6b-Cis) having Li⁺, Na⁺, and K⁺as cations, respectively, showed no difference in their effects, and ahigh discharge capacity (0° C.) after cycles was able to be obtained forall. Similarly, comparisons of the ionic complexes (1a-Cis), (6c-Cis),and (6d-Cis) having Li⁺, TMPA, and PP13 as cations, respectively,revealed that Li⁺ showed the best results although TMPA and PP13 showedsome effects (Example 1-21 was compared with Examples 1-34, 1-35). Thismay be because the content of anion sides as the effective moieties wasdecreased due to the large molecular weights of the cations of TMPA andPP13, and because some of TMPA and PP13 were reductively or oxidativelydecomposed, and decomposition residues were deposited as highlyresistive materials on the surface of an electrode.

As shown in Example 1-36, (1c-Cis) in which the central element of P wasreplaced with Si had a low solubility, and was not sufficientlydissolved at 1.0 mass %, but showed relatively good effects when addedat 0.8 mass %. Moreover, as shown in Examples 1-37 to 1-41, addition ofthe difluoro ionic complexes (6a-Trans, 6b-Trans, 6c-Trans, and6d-Trans) in the trans configuration having different cation species andthe difluoro ionic complex (1c-Trans) in the trans configuration inwhich the central element of P was replaced with Si can similarlyprovide a higher discharge capacity (0° C.) after prolonged cycles at60° C. and a higher 5C-rate characteristic after prolonged cycles at 60°C. as compared with Comparative Example 1-1.

Further, Examples 1-1 to 1-41, including the cyclic phosphazene compound(II-1-5), were able to prevent expansion of the cells during charge to alower level as compared with Comparative Examples 1-1 to 1-3. As shownin Examples 1-7 to 1-11, the more the amount of (II-1-5) increased, thelower the level to which expansion of the cells were able to beprevented.

Further, Examples 1-9 to 1-11, including 5 mass % or more of the cyclicphosphazene compound (II-1-5), were superior to Comparative Example 1-1in the combustibility test and were able to be evaluated asflame-retardant or more excellent. [Preparation of nonaqueouselectrolytic solutions: Nos. 2-1 to 2-16 and comparative electrolyticsolutions Nos. 2-1 to 2-8]

The nonaqueous electrolytic solutions Nos. 2-1 to 2-16 according to thepresent invention and the comparative electrolytic solutions Nos. 2-1 to2-8 were prepared in a similar way as in the nonaqueous electrolyticsolution No. 1-1.

That is, in a dry box under a nitrogen atmosphere of a dew point of −50°C. or less, LiPF₆ as an electrolyte was dissolved and prepared in apreheated and dissolved nonaqueous solvent of ethylene carbonate (EC)and ethylmethyl carbonate (EMC) (volume ratio 1:2) so that theconcentration of LiPF₆ was 1 mol/liter, and then various ioniccomplex/EMC solutions according to the present invention and the group(II) compounds as described above were added in a predetermined amountor were not added to prepare a variety of the nonaqueous electrolyticsolutions and the comparative electrolytic solutions shown in Table 3.

Examples 2-1 to 2-16 and Comparative Examples 2-1 to 2-8: Production andEvaluation of Nonaqueous Electrolytic Solution Batteries

Aluminum laminate housing cells (with a capacity of 30 mAh) includingthe test NMC positive electrode, the test graphite negative electrode,and a cellulose separator were respectively impregnated with a varietyof the nonaqueous electrolytic solutions and the comparativeelectrolytic solutions shown in Table 3 in a similar procedure as in thenonaqueous electrolytic solution batteries according to Examples 1-1 to1-41 to produce the nonaqueous electrolytic solution batteries accordingto Examples and Comparative Examples shown in Table 4. Each of thesenonaqueous electrolytic solution electrolytic solution batteries wassubjected to the following evaluations as described above as in Example1-1.

<Evaluation 1> Low-temperature property (0° C.) after 500 cycles at 60°C.

<Evaluation 2>5C-rate characteristic after 500 cycles at 60° C.

<Evaluation 3> Low-temperature property (0° C.) after stored at 60° C.

<Evaluation 4> Evaluation of expansion during charge

<Evaluation 5> Temperature rise value during overcharging test

<Evaluation 6> Evaluation of combustibility

Evaluations 1 to 3 of the nonaqueous electrolytic solution batteries areshown in Table 4 as relative values when the results in Evaluations 1 to3 of the nonaqueous electrolytic solution battery according toComparative Example 1-1 are taken as 100.

TABLE 3 Trans Tetrafluoro isomer/ complex/ Group (I) Group (III) CisGroup (IV) Cis compound Content Content compound Content isomer compoundContent isomer (Cis (mass Group (II) (mass Trans (mass (mass Tetrafluoro(mass (mass Electrolytic solution No, isomer) %) compound %) isomer %)ratio) complex %) ratio) Electrolytic solution No. 2-1 (1a-Cis) 1.0(II-2-1) 2.5 — — — — — — Electrolytic solution No. 2-2 1.0 2.5(1a-Trans) 0.004 0.004 (5a-Tetra) 0.14 0.14 Electrolytic solution No.2-3 1.0 (II-3-14) 1.5 — — — — — — Electrolytic solution No. 2-4 1.0 1.5(1a-Trans) 0.004 0.004 (5a-Tetra) 0.14 0.14 Electrolytic solution No.2-5 1.0 (II-4-2) 2.0 — — — — — — Electrolytic solution No. 2-6 1.0 2.0(1a-Trans) 0.004 0.004 (5a-Tetra) 0.14 0.14 Electrolytic solution No.2-7 1.0 (II-5-1) 15.0 — — — — — — Electrolytic solution No. 2-8 1.0 15.0(1a-Trans) 0.004 0.004 (5a-Tetra) 0.14 0.14 Electrolytic solution No.2-9 1.0 (II-6-1) 20.0 — — — — — — Electrolytic solution No. 2-10 1.020.0 (1a-Trans) 0.004 0.004 (5a-Tetra) 0.14 0.14 Electrolytic solutionNo. 2-11 1.0 (II-7-1) 20.0 — — — — — — Electrolytic solution No. 2-121.0 20.0 (1a-Trans) 0.004 0.004 (5a-Tetra) 0.14 0.14 Electrolyticsolution No. 2-13 1.0 (II-8-1) 10.0 — — — — — — Electrolytic solutionNo. 2-14 1.0 10.0 (1a-Trans) 0.004 0.004 (5a-Tetra) 0.14 0.14Electrolytic solution No. 2-15 1.0 (II-1-5) 10.0 — — — — — —Electrolytic solution No. 2-16 1.0 10.0 (1a-Trans) 0.004 0.004(5a-Tetra) 0.14 0.14 Comparative electrolytic — — (II-2-1) 2.5(1a-Trans) 1.0 — (5a-Tetra) 0.14 — solution No. 2-1 Comparativeelectrolytic — — (II-3-14) 1.5 (1a-Trans) 1.0 — (5a-Tetra) 0.14 —solution No. 2-2 Comparative electrolytic — — (II-4-2) 2.0 (1a-Trans)1.0 — (5a-Tetra) 0.14 — solution No. 2-3 Comparative electrolytic — —(II-5-1) 15.0 (1a-Trans) 1.0 — (5a-Tetra) 0.14 — solution No. 2-4Comparative electrolytic — — (II-6-1) 20.0 (1a-Trans) 1.0 — (5a-Tetra)0.14 — solution No. 2-5 Comparative electrolytic — — (II-7-1) 20.0(1a-Trans) 1.0 — (5a-Tetra) 0.14 — solution No. 2-6 Comparative — —(II-8-1) 10.0 (1a-Trans) 1.0 — (5a-Tetra) 0.14 — electrolytic solutionNo. 2-7 Comparative electrolytic — — (II-1-5) 10.0 (1a-Trans) 1.0 —(5a-Tetra) 0.14 — solution No. 2-8

TABLE 4 (Positive electrode; NMC Negative electrode; Graphite)Low-temperature 5C-rate Low-temperature property characteristic property(0° C.) (25° C.) (0° C.) Expansion Temperature after prolonged afterprolonged after stored rate rise value Combustibility Electrolyticsolution No, cycles at 60° C. cycles at 60° C. at 60° C. (%) (K) testExample 2-1 Electrolytic solution No. 2-1 134.9 136.5 121.3 5.8 — —Example 2-2 Electrolytic solution No. 2-2 135.4 137.4 122.5 6.7 — —Example 2-3 Electrolytic solution No. 2-3 129.4 133.5 110.6 — 38.4 —Example 2-4 Electrolytic solution No. 2-4 129.9 133.8 111.1 — 37.6 —Example 2-5 Electrolytic solution No. 2-5 130.6 134.8 112.7 — 41.0 —Example 2-6 Electrolytic solution No. 2-6 131.0 135.1 113.3 — 41.8 —Example 2-7 Electrolytic solution No. 2-7 134.5 136.8 117.9 — — Non-combustible Example 2-8 Electrolytic solution No. 2-8 135.1 137.1 118.3— — Non- combustible Example 2-9 Electrolytic solution No. 2-9 132.7132.5 114.6 — — Non- combustible Example 2-10 Electrolytic solution No.2-10 133.2 133.0 115.1 — — Non- combustible Example 2-11 Electrolyticsolution No. 2-11 133.4 136.4 117.4 — — Non- combustible Example 2-12Electrolytic solution No. 2-12 133.7 136.8 117.6 — — Non- combustibleExample 2-13 Electrolytic solution No. 2-13 134.3 137.9 114.2 — — Non-combustible Example 2-14 Electrolytic solution No. 2-14 134.9 138.4114.6 — — Non- combustible Example 2-15 Electrolytic solution No. 2-15131.6 133.6 117.6 — — Non- combustible Example 2-16 Electrolyticsolution No. 2-16 132.0 133.9 117.9 — — Non- combustible ComparativeComparative electrolytic 129.6 133.6 114.5 8.3 — — Example 2-1 solutionNo. 2-1 Comparative Comparative electrolytic 124.7 128.9 109.4 — 39.6 —Example 2-2 solution No. 2-2 Comparative Comparative electrolytic 125.4129.3 110.5 — 44.6 — Example 2-3 solution No. 2-3 ComparativeComparative electrolytic 129.8 132.6 113.3 — — Non- Example 2-4 solutionNo. 2-4 combustible Comparative Comparative electrolytic 128.0 131.8113.6 — — Non- Example 2-5 solution No. 2-5 combustible ComparativeComparative electrolytic 128.6 131.9 114.0 — — Non- Example 2-6 solutionNo. 2-6 combustible Comparative Comparative electrolytic 129.6 133.2110.7 — — Non- Example 2-7 solution No. 2-7 combustible ComparativeComparative electrolytic 130.3 132.8 115.8 — — Non- Example 2-8 solutionNo. 2-8 combustible(Regarding Examples 2-1 to 2-16)

As seen from the results in Tables 3 to 4, the nonaqueous electrolyticsolution batteries including the difluoro ionic complex (1a-Cis) in thecis configuration from Synthesis Example 1 according to Example and thegroup (II) compound selected from the siloxane compound (II-2-1), thearomatic compound (II-3-14), the cyclohexene compound (II-4-2), thephosphoric acid ester compound (II-5-1), the fluorinated linear ethercompound (II-6-1), the fluorinated cyclic ether compound (II-7-1), theboric acid ester compound (II-8-1), and the cyclic phosphazene compound(II-1-5) showed a higher discharge capacity (0° C.) after prolongedcycles at 60° C. and a higher 5C-rate characteristic after prolongedcycles at 60° C. as compared with the nonaqueous electrolytic solutionbattery including neither the above ionic complex nor the group (II)compound (Comparative Example 1-1).

Further, comparison of Example 2-2 with Comparative Example 2-1, Example2-4 with Comparative Example 2-2, Example 2-6 with Comparative Example2-3, Example 2-8 with Comparative Example 2-4, Example 2-10 withComparative Example 2-5, Example 2-12 with Comparative Example 2-6,Example 2-14 with Comparative Example 2-7, or Example 2-16 withComparative Example 2-8 revealed that the nonaqueous electrolyticsolution battery including the difluoro ionic complex (1a-Cis) in thecis configuration and the group (II) compound showed better results thanthe nonaqueous electrolytic solution battery including the difluoroionic complex (1a-Trans) in the trans configuration and the group (II)compound.

Further, comparison of Example 2-1 with Example 2-2, Example 2-3 withExample 2-4, Example 2-5 with Example 2-6, Example 2-7 with Example 2-8,Example 2-9 with Example 2-10, Example 2-11 with Example 2-12, Example2-13 with Example 2-14, or Example 2-15 with Example 2-16 revealed that,as compared with the nonaqueous electrolytic solution battery includingthe difluoro ionic complex (1a-Cis) in the cis configuration and thegroup (II) compound, the nonaqueous electrolytic solution batteryfurther including the difluoro ionic complex (1a-Trans) in the transconfiguration and the tetrafluoro ionic complex (5a-Tetra) was excellentin Evaluations 1 to 3.

Further, Examples 2-1 and 2-2, including the siloxane compound (II-2-1),were able to prevent expansion of the cells during charge as comparedwith Comparative Example 1-1, not including the siloxane compound(II-2-1).

Further, Examples 2-3 and 2-4, including the aromatic compound(II-3-14), and Examples 2-5 and 2-6, including the cyclohexene compound(II-4-2), were able to prevent temperature rise during overcharging ascompared with Comparative Example 1-1, not including these.

Further, Examples 2-7 and 2-8, including the phosphoric acid estercompound (II-5-1); Examples 2-9 and 2-10, including the fluorinatedlinear ether compound (II-6-1); Examples 2-11 and 2-12, including thefluorinated cyclic ether compound (II-7-1); Examples 2-13 and 2-14,including the boric acid ester compound (II-8-1); and Examples 2-15 and2-16, including the cyclic phosphazene compound (II-1-5), showednon-combustibility in the combustibility test and were able to make theelectrolytic solution more flame-retardant as compared with ComparativeExample 1-1, not including these.

Example 3—Positive Electrode: NCA Positive Electrode

With regard to Example 3 and Comparative Example 3, a positive-electrodeactive material (LiNi_(0.85)Co_(0.10)Al_(0.05)O₂ (NCA)) was used placeof the positive-electrode active material (NMC) used in Example 1.

<Production of NCA Positive Electrode>

A LiNi_(0.85)CO_(0.10)Al_(0.05)O₂ (NCA) powder (Todakogyo Corp.) andacetylene black (electrically conductive agent) were dry-mixed, anduniformly dispersed and mixed into NMP where PVDF as a binding agent waspre-dissolved, and NMP for adjusting the viscosity was further added toprepare a NCA mixture paste. The resulting paste was applied to analuminum foil (current collector), dried, and pressurized. Then thealuminum foil was processed into a predetermined size to obtain a testNCA positive electrode. The ratio of solid contents in the positiveelectrode was NCA:electrically conductive agent:PVDF=85:5:10 (by themass ratio).

<Production of Nonaqueous Electrolytic Solution Batteries>

Aluminum laminate housing cells (with a capacity of 30 mAh) includingthe above test NMC positive electrode, the test graphite negativeelectrode, and a cellulose separator were respectively impregnated withone of the various nonaqueous electrolytic solutions and the variouscomparative electrolytic solutions shown in Table 5 to produce thenonaqueous electrolytic solution batteries according to Example 3 andComparative Example 3. It is noted that Table 5 summarizes thecompositions of the above electrolytic solutions.

TABLE 5 Trans Tetrafluoro isomer/ complex/ Group (I) Group (III) CisGroup (IV) Cis compound Content Content compound Content isomer compoundContent isomer (Cis (mass Group (II) (mass Trans (mass (mass Tetrafluoro(mass (mass Electrolytic solution No, isomer) %) compound %) isomer %)ratio) complex %) ratio) Electrolytic solution No. 1-4 (1a-Cis) 1.0(II-1-5) 3.0 — — — — — — Electrolytic solution No. 1-21 (1a-Trans) 0.0040.004 (5a-Tetra) 0.14 0.14 Electrolytic solution No. 2-3 (1a-Cis) 1.0(II-3-14) 1.5 — — — — — — Electrolytic solution No. 2-4 (1a-Trans) 0.0040.004 (5a-Tetra) 0.14 0.14 Electrolytic solution No. 2-7 (1a-Cis) 1.0(II-5-1) 15.0 — — — — — — Electrolytic solution No. 2-8 (1a-Trans) 0.0040.004 (5a-Tetra) 0.14 0.14 Comparative electrolytic — — — — — — — — — —solution No. 1-1 Comparative electrolytic (1a-Cis) 1.0 — — — — — — — —solution No. 1-2 Comparative electrolytic — — (II-1-5) 3.0 (1a-Trans)1.0 — (5a-Tetra) 0.14 — solution No. 1-5 Comparative electrolytic — —(II-3-14) 1.5 (1a-Trans) 1.0 — (5a-Tetra) 0.14 — solution No. 2-2Comparative electrolytic — — (II-5-1) 15.0 (1a-Trans) 1.0 — (5a-Tetra)0.14 — solution No. 2-4

Example 3 and Comparative Example 3: Evaluation of Test Cells

<Evaluation 1> Low-Temperature Property (0° C.) after 500 Cycles at 60°C.

Each of the nonaqueous electrolytic solution batteries according toExample 3 and Comparative Example 3 was evaluated as in Evaluation 1performed for the nonaqueous electrolytic solution battery according toExample 1-1. However, the charge upper limit voltage was changed from4.3 V to 4.2 V in the initial charge and discharge as conditioning at anenvironmental temperature of 25° C. and in the charge-discharge cycle.Furthermore, after this conditioning, the charge upper limit voltage waschanged from 4.3 V to 4.2 V when performing 500 cycles at anenvironmental temperature of 60° C. Moreover, constant-current andconstant-voltage charge was performed to 4.2 V instead of 4.3 at 0° C.and a 0.2 C rate. The capacity obtained at that time was considered asthe low-temperature property (0° C.) after prolonged cycles at 60° C.

<Evaluation 2>5C-Rate Characteristic after 500 Cycles at 60° C.

Each of the nonaqueous electrolytic solution batteries according toExample 3 and Comparative Example 3 was evaluated as in Evaluation 2preformed for the nonaqueous electrolytic solution battery according toExample 1-1. However, constant-current and constant-voltage charge wasperformed to 4.2 V instead of 4.3 V at 25° C. and a 5 C rate. Thecapacity obtained at that time was considered as the 5C-ratecharacteristic (25° C.) after prolonged cycles at 60° C.

<Evaluation 3> Low-Temperature Property (0° C.) after Stored at 60° C.

For each of the nonaqueous electrolytic solution batteries according toExample 3 and Comparative Example 3, storage tests were performed at anenvironmental temperature of 60° C. (stored for 10 days afterconstant-current and constant-voltage charge to 4.2 V instead of 4.3 V),which was Evaluation 3 performed for the nonaqueous electrolyticsolution battery according to Example 1-1. However, constant-current andconstant-voltage charge was performed to 4.2 V instead of 4.3 V at 0° C.and a 2 C rate. The capacity obtained at that time was considered as thelow-temperature property (0° C.) after stored at 60° C.

Evaluations 1 to 3 of the nonaqueous electrolytic solution batteriesaccording to Example 3 and Comparative Example 3 are shown in Table 6 asrelative values when Evaluations 1 to 3 of the nonaqueous electrolyticsolution battery according to Comparative Example 3-1 are taken as 100.

<Evaluation 4> Evaluation of Expansion During Charge

Evaluations were performed as in Example 1-1 except that charge to 4.3 Vwas changed to charge to 4.2 V.

<Evaluation 5> Temperature Rise Value During Overcharging Test, and

<Evaluation 6> Evaluation of Combustibility

Evaluations were performed as in Example 1-1.

TABLE 6 (Positive electrode; NCA Negative electrode; Graphite)Low-temperature 5C-rate Low-temperature property characteristic property(0° C.) (25° C.) (0° C.) Expansion Temperature after prolonged afterprolonged after stored rate rise value Combustibility Electrolyticsolution No, cycles at 60° C. cycles at 60° C. at 60° C. (%) (K) testExample 3-1 Electrolytic solution No. 1-4 132.4 137.6 117.5 5.0 — —Example 3-2 Electrolytic solution No. 1-21 133.0 138.1 117.8 5.0 — —Example 3-3 Electrolytic solution No. 2-3 128.2 132.3 116.4 — 43.1 —Example 3-4 Electrolytic solution No. 2-4 128.7 132.8 116.7 — 42.3 —Example 3-5 Electrolytic solution No. 2-7 133.9 137.0 116.9 — — Non-combustible Example 3-6 Electrolytic solution No. 2-8 134.3 137.4 117.3— — Non- combustible Comparative Comparative electrolytic 100.0 100.0100.0 12.5 >99.9 Combustible Example 3-1 solution No. 1-1 ComparativeComparative electrolytic 125.8 131.4 111.1 10.8 >99.9 CombustibleExample 3-2 solution No. 1-2 Comparative Comparative electrolytic 127.6132.0 113.5 6.7 — — Example 3-3 solution No. 1-5 Comparative Comparativeelectrolytic 123.7 127.6 108.9 — 43.6 — Example 3-4 solution No. 2-2Comparative Comparative electrolytic 129.1 132.1 112.8 — — Non- Example3-5 solution No. 2-4 combustible

Example 4—Positive Electrode: LMO Positive Electrode

With regard to Example 4, a LiMn_(1.95)Al_(0.05)O₄ (LMO) powder as alithium-manganese composite oxide having a spinel structure was used asa positive-electrode active material in place of the positive-electrodeactive material (LiNi_(0.85)Co_(0.10)Al_(0.05)O₂ (NCA)) used in Example3.

<Production of LMO Positive Electrode>

A LiMn_(1.95)Al_(0.05)O₄ (LMO) powder (Todakogyo Corp.) and acetyleneblack (electrically conductive agent) were dry-mixed, and uniformlydispersed and mixed into NMP where PVDF as a binding agent waspre-dissolved, and NMP for adjusting the viscosity was further added toprepare a LMO mixture paste. The resulting paste was applied to analuminum foil (current collector), dried, and pressurized. Then thealuminum foil was processed into a predetermined size to obtain a testLMO positive electrode. The ratio of solid contents in the positiveelectrode was LMO:electrically conductive agent:PVDF=85:5:10 (by themass ratio).

<Production of Nonaqueous Electrolytic Solution Batteries>

Aluminum laminate housing cells (with a capacity of 30 mAh) includingthe above test LMO positive electrode, the test graphite negativeelectrode, and a separator consisting of a microporouspolypropylene-polyethylene two-layer film (whose polypropylene side wasarranged on the positive electrode side) were impregnated with each ofthe various nonaqueous electrolytic solutions and the variouscomparative electrolytic solutions shown in Table 5 to produce thenonaqueous electrolytic solution batteries according to Example 4 andComparative Example 4.

Each of these nonaqueous electrolytic solution electrolytic solutionbatteries was subjected to the following evaluations as described aboveas in Example 3 and Comparative Example 3.

<Evaluation 1> Low-temperature property (0° C.) after 500 cycles at 60°C.

<Evaluation 2>5C-rate characteristic after 500 cycles at 60° C.

<Evaluation 3> Low-temperature property (0° C.) after stored at 60° C.

<Evaluation 4> Evaluation of expansion during charge

<Evaluation 5> Temperature rise value during overcharging test

<Evaluation 6> Evaluation of combustibility

Evaluations 1 to 3 of the nonaqueous electrolytic solution batteriesaccording to Example 4 and Comparative Example 4 are shown in Table 7 asrelative values when the results in Evaluations 1 to 3 of the nonaqueouselectrolytic solution battery according to Comparative Example 4-1 aretaken as 100.

TABLE 7 (Positive electrode; LMO Negative electrode; Graphite)Low-temperature 5C-rate Low-temperature property characteristic property(0° C.) (25° C.) (0° C.) Expansion Temperature after prolonged afterprolonged after stored rate rise value Combustibility Electrolyticsolution No, cycles at 60° C. cycles at 60° C. at 60° C. (%) (K) testExample 4-1 Electrolytic solution No. 1-4 133.5 138.5 118.5 5.0 — —Example 4-2 Electrolytic solution No. 1-21 133.9 139.4 118.7 4.2 — —Example 4-3 Electrolytic solution No. 2-3 129.2 133.4 117.5 — 45.3 —Example 4-4 Electrolytic solution No. 2-4 129.8 133.6 117.8 — 44.8 —Example 4-5 Electrolytic solution No. 2-7 134.7 137.9 118.0 — — Non-combustible Example 4-6 Electrolytic solution No. 2-8 135.4 138.3 118.3— — Non- combustible Comparative Comparative electrolytic 100.0 100.0100.0 11.7 >99.9 Combustible Example 4-1 solution No. 1-1 ComparativeComparative electrolytic 126.7 132.3 112.1 10.0 >99.9 CombustibleExample 4-2 solution No. 1-2 Comparative Comprative electrolytic 128.4133.0 114.4 5.8 — — Example 4-3 solution No. 1-5 Comparative Comparativeelectrolytic 124.8 128.6 109.6 — 46.5 — Example 4-4 solution No. 2-2Comparative Comparative electrolytic 129.8 133.2 113.7 — — Non- Example4-5 solution No. 2-4 combustible

Example 5—Positive Electrode: LFP Positive Electrode

With regard to Example 5, a LiFePO₄ (LFP) powder as a lithium-containingolivine-type phosphate salt was used as a positive-electrode activematerial in place of the positive-electrode active material(LiMn_(1.95)Al_(0.05)O₄ (LMO)) used in Example 4.

<Production of LFP Positive Electrode>

A LiFePO₄ (LFP) powder, acetylene black (electrically conductive agent1), and vapor-grown carbon fiber (VGCF®-H, Showa Denko K. K.)(electrically conductive agent 2) were dry-mixed, and uniformlydispersed and mixed into NMP in which PVDF as a binding agent waspre-dissolved, and NMP for adjusting the viscosity was further added toprepare an LFP mixture paste. The resulting paste was applied to analuminum foil (current collector), dried, and pressurized. Then thealuminum foil was processed into a predetermined size to obtain a testLFP positive electrode. The ratio of solid contents in the negativeelectrode was LFP:electrically conductive agent 1:electricallyconductive agent 2:PVDF=85:4:1:10 (by the mass ratio).

<Production of Nonaqueous Electrolytic Solution Batteries>

Aluminum laminate housing cell (with a capacity of 30 mAh) including theabove test LFP positive electrode, the test graphite negative electrode,and a microporous polypropylene-polyethylene double layered separatorwere respectively impregnated with one of the various nonaqueouselectrolytic solutions and the various comparative electrolyticsolutions shown in Table 5 to produce the nonaqueous electrolyticsolution batteries according to Examples 5-1 to 5-6 and ComparativeExamples 5-1 to 5-5 in a similar way as in Example 4-1.

Example 5 and Comparative Example 5: Evaluation of Test Cells

<Evaluation 1> Low-Temperature Property (0° C.) after 500 Cycles at 60°C.

Each of the nonaqueous electrolytic solution batteries according toExample 5 and Comparative Example 5 was evaluated as described below.

First, the cells produced as described above were subjected toconditioning at an environmental temperature of 25° C. under thefollowing conditions. That is, constant-current and constant-voltagecharge was performed as the initial charge/discharge to a charge upperlimit voltage of 3.6 V at a 0.1 C rate (3 mA), and discharge was thenperformed to a discharge cutoff voltage of 2.0 V at a constant currentof a 0.2 C rate (6 mA), and subsequently the following charge-dischargecycle was repeated for 3 times: constant-current and constant-voltagecharge was performed to a charge upper limit voltage of 3.6 V at a 0.2 Crate (6 mA), and discharge was then performed to a discharge cutoffvoltage of 2.0 V at a constant current of a 0.2 C rate (6 mA).

After this conditioning, charge and discharge tests were performed at anenvironmental temperature of 60° C. The following charge-discharge cyclewas repeated for 500 times: constant-current and constant-voltage chargewas performed at a 3 C rate (90 mA) to a charge upper limit voltage of3.6 V, and discharge was performed at a constant current of a 3 C rate(90 mA) to a discharge cutoff voltage of 2.0 V.

Next, the nonaqueous electrolytic solution batteries were cooled to 25°C., and again discharged to 2.0 V. Then constant-current andconstant-voltage charge was performed to 3.6 V at a 0.2 C rate at 0° C.Further, discharge was performed at a constant current of a 5 C rate(150 mA) to a discharge cutoff voltage of 2.0 V, and the capacityobtained at that time was taken as the low-temperature property (0° C.)after prolonged cycles at 60° C.

<Evaluation 2>5C-Rate Characteristic after 500 Cycles at 60° C.

After performing 500 cycles at an environmental temperature of 60° C. inEvaluation 1 as described above, the nonaqueous electrolytic solutionbatteries were cooled to 25° C., and then again discharged to 2.0 V.Subsequently constant-current and constant-voltage charge was performedto 3.6 V at a 5 C rate at 25° C. Further, discharge was performed at aconstant current of a 5 C rate (150 mA) to a discharge cutoff voltage of2.0 V, and the capacity obtained at that time was taken as the 5C-ratecharacteristic (25° C.) after prolonged cycles at 60° C.

<Evaluation 3> Low-Temperature Property (0° C.) after Stored at 60° C.

Each of the nonaqueous electrolytic solution batteries according toExample 5 and Comparative Example 5 was subjected to storage tests(stored for 10 days after charged to 3.6 V) at an environmentaltemperature of 60° C. Next, the nonaqueous electrolytic solutionbatteries were cooled to 25° C., and again discharged to 2.0 V. Thenconstant-current and constant-voltage charge was performed to 3.6 V at a0.2 C rate at 0° C. Further, discharge was performed at a constantcurrent of a 5C rate (150 mA) to a discharge cutoff voltage of 2.0 Vwhile maintaining the temperature at 0° C., and the capacity obtained atthat time was taken as the low-temperature property (0° C.) after storedat 60° C.

Evaluations 1 to 3 of the nonaqueous electrolytic solution batteriesaccording to Example 5 and Comparative Example 5 are shown in Table 8 asrelative values when Evaluations 1 to 3 of the nonaqueous electrolyticsolution battery according to Comparative Example 5-1 are taken as 100.

<Evaluation 4> Evaluation of Expansion During Charge

Evaluations were performed as in Example 1-1 except that charge to 4.3 Vwas changed to charge to 3.6 V.

<Evaluation 5> Temperature Rise Value During Overcharging Test, and

<Evaluation 6> Evaluation of Combustibility

Evaluations were performed as in Example 1-1.

TABLE 8 (Positive electrode; LFP Negative electrode; Graphite)Low-temperature 5C-rate Low-temperature property characteristic property(0° C.) (25° C.) (0° C.) Expansion Temperature after prolonged afterprolonged after stored rate rise value Combustibility Electrolyticsolution No, cycles at 60° C. cycles at 60° C. at 60° C. (%) (K) testExample 5-1 Electrolytic solution No. 1-4 131.0 135.7 116.3 6.7 — —Example 5-2 Electrolytic solution No. 1-21 131.5 136.2 116.7 6.7 — —Example 5-3 Electrolytic solution No. 2-3 126.6 130.5 114.9 — 37.6 —Example 5-4 Electrolytic solution No. 2-4 127.1 130.9 115.2 — 36.8 —Example 5-5 Electrolytic solution No. 2-7 132.0 135.2 114.8 — — Non-combustible Example 5-6 Electrolytic solution No. 2-8 132.5 135.7 115.2— — Non- combustible Comparative Comparative electrolytic 100.0 100.0100.0 14.2 >99.9 Combustible Example 5-1 solution No. 1-1 ComparativeComparative electrolytic 123.9 129.5 109.3 12.5 >99.9 CombustibleExample 5-2 solution No. 1-2 Comparative Comparative electrolytic 125.7130.2 111.6 8.3 — — Example 5-3 solution No. 1-5 Comparative Comparativeelectrolytic 121.8 125.1 107.6 — 39.4 — Example 5-4 solution No. 2-2Comparative Comparative electrolytic 127.4 130.7 110.0 — — Non- Example5-5 solution No. 2-4 combustible(Regarding Examples 3 to 5)

As seen from the results in above, even in a case where NCA, LMO, or LFPis used instead of NMC as a positive-electrode active material inExamples 3-1 to 3-6, Examples 4-1 to 4-6, and Examples 5-1 to 5-6, thenonaqueous electrolytic solution batteries including the difluoro ioniccomplex (1a-Cis) in the cis configuration from Synthesis Example 1 asthe group (I) compound according to Example and the cyclic phosphazenecompound (II-1-5), the aromatic compound (II-3-14), or the phosphoricacid ester compound (II-5-1) as the group (II) compound were found to beexcellent in Evaluations 1 to 3 as compared with the nonaqueouselectrolytic solution batteries not including these (ComparativeExamples 3-1, 4-1, and 5-1).

Further, the nonaqueous electrolytic solution batteries including thedifluoro ionic complex (1a-Cis) in the cis configuration and the group(II) compound were found to be excellent in Evaluations 1 to 3 ascompared with the nonaqueous electrolytic solution batteries includingthe difluoro ionic complex (1a-Trans) in the trans configuration and thegroup (II) compound.

Further, Examples including the cyclic phosphazene compound (II-1-5)were able to prevent expansion of the cells during charge as comparedwith Comparative Examples not including this.

Further, Examples including the aromatic compound (II-3-14) were able toprevent temperature rise during overcharging as compared withComparative Examples not including this.

Further, Examples including the phosphoric acid ester compound (II-5-1)showed non-combustibility in the combustibility test and were able tomake the electrolytic solution more flame-retardant as compared withComparative Examples not including this.

The above results demonstrated that the nonaqueous electrolyticsolutions according to the present invention showed good effects in anyof the cases where the following oxides were used as a positiveelectrode: a lithium-transition metal composite oxide containing atleast one metal of nickel, manganese, and cobalt and having a layeredstructure; a lithium-manganese composite oxide having the spinelstructure; and a lithium-containing olivine-type iron phosphate.

That is, these results clearly demonstrate that the nonaqueouselectrolytic solution according to the present invention, and batteriesusing this can show high output characteristics at low temperature evenafter the batteries are used to some extent, and can also showsufficient performance again at low temperature even after stored athigh temperature regardless of types of positive electrodes. Further,the nonaqueous electrolytic solution according to the present inventionand batteries using this are capable of exerting effects of improvingsafety of batteries such as flame retardancy, prevention of expansionduring charge and discharge, or prevention of overcharging, depending onthe combinedly used compound shown in group II.

Example 6—Negative Electrode: Amorphous Carbon Negative Electrode

With regard to Example 6, an amorphous carbon powder as a carbonmaterial having a d value in the lattice plane (002) of more than 0.340nm as determined by X ray diffraction was used as a negative-electrodeactive material in place of the negative-electrode active material (agraphite powder) used in Example 1.

<Production of Amorphous Carbon Negative Electrode>

Carbotron® P from Kureha Corporation as an amorphous carbon powder wasuniformly dispersed and mixed into NMP in which PVDF as a binding agentwas pre-dissolved, and NMP for adjusting the viscosity was then furtheradded to prepare an amorphous carbon mixture paste. The above paste wasapplied to a copper foil (current collector), dried, and pressurized.Then the copper foil was processed into a predetermined size to obtain atest amorphous carbon negative electrode. The ratio of solid contents inthe negative electrode was amorphous carbon powder:PVDF=90:10 (by themass ratio).

(Preparation of Nonaqueous Electrolytic Solutions)

The nonaqueous electrolytic solutions Nos. 3-1 to 3-6 according to thepresent invention were prepared in a similar way as in the nonaqueouselectrolytic solution No. 1-1 except that FEC was added as a nonaqueoussolvent.

That is, LiPF₆ as an electrolyte was dissolved and prepared in EC, EMC,and FEC (volume ratio 25:70:5/mass ratio 29.7:63.6:6.7 or volume ratio20:70:10/mass ratio 23.6:63.1:13.3) as a nonaqueous solvent or anonaqueous solvent of EC and EMC (volume ratio 30:70/mass ratio35.9:64.1) to which FEC was not added so that the concentration of LiPF₆was 1.2 mol/L, and then various ionic complex/EMC solutions according tothe present invention and the group (II) compounds were added to preparethe nonaqueous electrolytic solutions Nos. 3-1 to 3-6 and comparativeelectrolytic solutions Nos. 3-1 to 3-11 shown in Table 9 below.

<Production of Nonaqueous Electrolytic Solution Batteries>

Aluminum laminate housing cells (with a capacity of 30 mAh) includingthe above test NMC positive electrode, the test amorphous carbonnegative electrode, and a microporous polypropylene-polyethylene doublelayered separator were respectively impregnated with one of the variousnonaqueous electrolytic solutions and the various comparativeelectrolytic solutions shown in Table 9 to produce the nonaqueouselectrolytic solution batteries according to Example 6 and ComparativeExample 6.

TABLE 9 Group (II) Li salt Nonaqueous solvent compound LiPF₆ EC EMC FECCis Content Group (II) Electrolytic solution No, (mol/liter) (mass %)(mass %) (mass %) isomer (mass %) compound Electrolytic solution 1.229.7 63.6 6.7 (1a-Cis) 1.2 (II-1-5) No. 3-1 Electrolytic solution(II-3-14) No. 3-2 Electrolytic solution (II-5-1) No. 3-3 Electrolyticsolution 1.2 23.6 63.1 13.3 (1a-Cis) 1.2 (II-1-5) No. 3-4 Electrolyticsolution (II-3-14) No. 3-5 Electrolytic solution (II-5-1) No. 3-6Comparative electrolytic 1.2 35.9 64.1 — — — — solution No. 3-1Comparative electrolytic 1.2 29.7 63.6 6.7 — — — solution No. 3-2Comparative electrolytic (1a-Cis) 1.2 — solution No. 3-3 Comparativeelectrolytic — — (II-1-5) solution No. 3-4 Comparative electrolytic — —(II-3-14) solution No. 3-5 Comparative electrolytic — — (II-5-1)solution No. 3-6 Comparative electrolytic 1.2 23.6 63.1 13.3 — — —solution No. 3-7 Comparative electrolytic (1a-Cis) 1.2 — solution No.3-8 Comparative electrolytic — — (II-1-5) solution No. 3-9 Comparativeelectrolytic — — (II-3-14) solution No. 3-10 Comparative electrolytic —— (II-5-1) solution No. 3-11 Tetra- Trans Group fluoro Group isomer/(IV) complex/ (III) Cis compound Cis compound isomer Tetra- isomerContent Trans Content (mass fluoro Content (mass Electrolytic solutionNo, (mass %) isomer (mass %) ratio) complex (mass %) ratio) Electrolyticsolution 3.6 (1a-Trans) 0.006 0.005 (5a-Tetra) 0.144 0.12 No. 3-1Electrolytic solution 1.8 No. 3-2 Electrolytic solution 18 No. 3-3Electrolytic solution 3.6 (1a-Trans) 0.006 0.005 (5a-Tetra) 0.144 0.12No. 3-4 Electrolytic solution 1.8 No. 3-5 Electrolytic solution 18 No.3-6 Comparative electrolytic — — — — — — — solution No. 3-1 Comparativeelectrolytic — — — — — — — solution No. 3-2 Comparative electrolytic — —— — — — — solution No. 3-3 Comparative electrolytic 3.6 (1a-Trans) 1.2 —(5a-Tetra) 0.144 — solution No. 3-4 Comparative electrolytic 1.8solution No. 3-5 Comparative electrolytic 18 solution No. 3-6Comparative electrolytic — — — — — — — solution No. 3-7 Comparativeelectrolytic — — — — — — — solution No. 3-8 Comparative electrolytic 3.6(1a-Trans) 1.2 — (5a-Tetra) 0.144 — solution No. 3-9 Comparativeelectrolytic 1.8 solution No. 3-10 Comparative electrolytic 18 solutionNo. 3-11

Example 6 and Comparative Example 6: Evaluation of Test Cells

<Evaluation 1> Low-Temperature Property (0° C.) after 500 Cycles at 60°C.

For each of the nonaqueous electrolytic solution batteries according toExample 6 and Comparative Example 6, conditioning and evaluation wereperformed as in Evaluation 1 performed for the nonaqueous electrolyticsolution batteries according to Example 3.

That is, constant-current and constant-voltage charge was performed asthe initial charge/discharge at an environmental temperature of 25° C.using the produced cells to a charge upper limit voltage of 4.2 V at a0.1 C rate (3 mA), and discharge was performed at a constant current ofa 0.2 C rate (6 mA) to a discharge cutoff voltage of 2.7 V.Subsequently, the following charge-discharge cycle was repeated for 3times: constant-current and constant-voltage charge was performed to acharge upper limit voltage of 4.2 V at a 0.2 C rate (6 mA), anddischarge was performed at a constant current of a 0.2 C rate (6 mA) toa discharge cutoff voltage of 2.7 V. After this conditioning, similarevaluation was performed except that when 500 cycles at an environmentaltemperature of 60° C. were performed, the discharge cutoff voltage waschanged from 3.0 V to 2.7 V, and when constant-current andconstant-voltage charge was performed to 4.2 V at a 0.2 C rate at 0° C.,and then discharge was performed while maintaining the temperature at 0°C., the discharge cutoff voltage was changed from 3.0 V to 2.7 V, anddischarge was performed at a constant current of a 5 C rate (150 mA).The capacity obtained at that time was considered as the low-temperatureproperty (0° C.) after prolonged cycles at 60° C.

<Evaluation 2>5C-Rate Characteristic after 500 Cycles at 60° C.

Each of the nonaqueous electrolytic solution batteries according toExample 6 and Comparative Example 6 was evaluated as in Evaluation 2performed for the nonaqueous electrolytic solution batteries accordingto Example 3. However, the discharge cutoff voltage was changed from 3.0V to 2.7 V upon discharge at a 5 C rate at 25° C. The capacity obtainedat that time was considered as the 5C-rate characteristic (25° C.) afterprolonged cycles at 60° C.

<Evaluation 3> Low-Temperature Property (0° C.) after Stored at 60° C.

Each of the nonaqueous electrolytic solution batteries according toExample 6 and Comparative Example 6 was subjected to storage tests(stored for 10 days after charged to 4.2 V at a constant current and aconstant voltage) at an environmental temperature of 60° C. as inEvaluation 3 performed for the nonaqueous electrolytic solutionbatteries according to Example 3. However, the discharge cutoff voltagewas changed from 3.0 V to 2.7 V upon discharge at a 5 C rate at 0° C.The capacity obtained at that time was considered as the low-temperatureproperty (0° C.) after stored at 60° C.

Evaluations 1 to 3 of the nonaqueous electrolytic solution batteriesaccording to Example 6 and Comparative Example 6 are shown in Table 10as relative values when Evaluations 1 to 3 of the nonaqueouselectrolytic solution battery according to Comparative Example 6-1 aretaken as 100.

<Evaluation 4> Evaluation of Expansion During Charge

Evaluations were performed as in Example 1-1 except that charge to 4.3 Vwas changed to charge to 4.2 V.

<Evaluation 5> Temperature Rise Value During Overcharging Test, and

<Evaluation 6> Evaluation of Combustibility

Evaluations were performed as in Example 1-1.

TABLE 10 (Positive electrode; NMC Negative electrode; Amorphous carbon)Low-temperature 5C-rate Low-temperature property characteristic property(0° C.) (25° C.) (0° C.) Expansion Temperature after prolonged afterprolonged after stored rate rise value Combustibility Electrolyticsolution No, cycles at 60° C. cycles at 60° C. at 60° C. (%) (K) testExample 6-1 Electrolytic solution No. 3-1 133.6 132.5 124.4 5.0 — —Example 6-2 Electrolytic solution No. 3-2 125.5 128.9 119.6 — 38.9 —Example 6-3 Electrolytic solution No. 3-3 133.3 131.8 122.3 — — Non-combustible Example 6-4 Electrolytic solution No. 3-4 137.0 131.4 128.84.2 — — Example 6-5 Electrolytic solution No. 3-5 131.6 130.2 123.9 —37.6 — Example 6-6 Electrolytic solution No. 3-6 135.4 132.6 125.4 — —Non- combustible Comparative Comparative electrolytic 100.0 100.0 100.012.5 >99.9 Combustible Example 6-1 solution No. 3-1 ComparativeComparative electrolytic 104.6 99.9 108.1 11.7 >99.9 Combustible Example6-2 solution No. 3-2 Comparative Comparative electrolytic 127.8 128.4119.6 10.0 >99.9 Combustible Example 6-3 solution No. 3-3 ComparativeComparative electrolytic 128.4 128.6 119.9 7.5 — — Example 6-4 solutionNo. 3-4 Comparative Comparative electrolytic 121.2 125.8 115.5 — 41.2 —Example 6-5 solution No. 3-5 Comparative Comparative electrolytic 128.6126.4 117.7 — — Non- Example 6-6 solution No. 3-6 combustibleComparative Comparative electrolytic 105.7 99.2 113.5 11.7 >99.9Combustible Example 6-7 solution No. 3-7 Comparative Comparativeelectrolytic 131.1 126.8 122.3 10.0 >99.9 Combustible Example 6-8solution No. 3-8 Comparative Comparative electrolytic 132.5 126.9 123.76.7 — — Example 6-9 solution No. 3-9 Comparative Comparativeelectrolytic 127.8 125.6 119.4 — 40.0 — Example 6-10 solution No. 3-10Comparative Comparative electrolytic 131.2 127.1 120.9 — — Non- Example6-11 solution No. 3-11 combustible

Example 7—Negative Electrode: (Mixture of Artificial Graphite+NaturalGraphite) Negative Electrode)

With regard to Example 7, a negative-electrode active material in whichan artificial graphite and natural graphite are mixed with each otherwas used in place of the negative-electrode active material (anamorphous carbon powder) used in Example 6.

<Production of Test (Mixture of Artificial Graphite+Natural Graphite)Negative Electrode>

An SCMG®-AR powder from Showa Denko K. K. as artificial graphite andnatural graphite particles (the mean particle size: 25 μm) from KansaiCoke and Chemicals Company, Limited. as natural graphite were uniformlydispersed and mixed into NMP in which PVDF as a binding agent waspre-dissolved, and NMP for adjusting the viscosity was then furtheradded to prepare a mixture paste of (artificial graphite+naturalgraphite) mixture. The above paste was applied to a copper foil (currentcollector), dried, and pressurized. Then the copper foil was processedinto a predetermined size to obtain a test (mixture of artificialgraphite+natural graphite) negative electrode. The ratio of solidcontents in the negative electrode was artificial graphitepowder:natural graphite powder:PVDF=72:18:10 (by the mass ratio).

<Production of Nonaqueous Electrolytic Solution Batteries>

Aluminum laminate housing cells (with a capacity of 30 mAh) includingthe above test NMC positive electrode, the test (mixture of artificialgraphite+natural graphite) negative electrode, and a microporouspolypropylene-polyethylene double layered separator were respectivelyimpregnated with one of the various nonaqueous electrolytic solutionsand the various comparative electrolytic solutions shown in Table 9 toproduce the nonaqueous electrolytic solution batteries according toExamples 7-1 to 7-6 and Comparative Examples 7-1 to 7-11 as in Example 6as described above.

<Production of Nonaqueous Electrolytic Solution Batteries>

Each of these nonaqueous electrolytic solution batteries was subjectedto the following evaluations as described above as in Example 1described above.

<Evaluation 1> Low-temperature property (0° C.) after 500 cycles at 60°C.

<Evaluation 2>5C-rate characteristic after 500 cycles at 60° C.

<Evaluation 3> Low-temperature property (0° C.) after stored at 60° C.

<Evaluation 4> Evaluation of expansion during charge

<Evaluation 5> Temperature rise value during overcharging test

<Evaluation 6> Evaluation of combustibility

Evaluations 1 to 3 of the nonaqueous electrolytic solution batteriesaccording to Example 7 and Comparative Example 7 are shown in Table 11as relative values when the results in Evaluations 1 to 3 of thenonaqueous electrolytic solution battery according to ComparativeExample 7-1 are taken as 100.

TABLE 11 (Positive electrode; NMC Negative electrode; Mixture ofartificial graphite + natural graphite) Low-temperature 5C-rateLow-temperature property characteristic property (0° C.) (25° C.) (0°C.) Expansion Temperature after prolonged after prolonged after storedrate rise value Combustibility Electrolytic solution No, cycles at 60°C. cycles at 60° C. at 60° C. (%) (K) test Example 7-1 Electrolyticsolution No. 3-1 136.6 135.4 127.8 8.3 — — Example 7-2 Electrolyticsolution No. 3-2 128.6 131.0 122.3 — 35.8 — Example 7-3 Electrolyticsolution No. 3-3 136.0 134.2 125.4 — — Non- combustible Example 7-4Electrolytic solution No. 3-4 139.4 133.9 130.7 7.5 — — Example 7-5Electrolytic solution No. 3-5 133.8 133.4 127.3 — 34.4 — Example 7-6Electrolytic solution No. 3-6 138.6 135.0 128.6 — — Non- combustibleComparative Comparative electrolytic 100.0 100.0 100.0 15.0 >99.9Combustible Example 7-1 solution No. 3-1 Comparative Comparativeelectrolytic 106.0 98.0 111.1 14.2 >99.9 Combustible Example 7-2solution No. 3-2 Comparative Comparative electrolytic 130.1 131.4 123.012.5 >99.9 Combustible Example 7-3 solution No. 3-3 ComparativeComparative electrolytic 131.2 131.4 122.0 10.0 — — Example 7-4 solutionNo. 3-4 Comparative Comparative electrolytic 123.9 128.8 118.3 — 39.3 —Example 7-5 solution No. 3-5 Comparative Comparative electrolytic 131.4129.3 120.8 — — Non- Example 7-6 solution No. 3-6 combustibleComparative Comparative electrolytic 111.5 96.6 116.5 13.3 >99.9Combustible Example 7-7 solution No. 3-7 Comparative Comparativeelectrolytic 133.8 129.8 125.4 11.7 >99.9 Combustible Example 7-8solution No. 3-8 Comparative Comparative electrolytic 135.6 130.0 126.69.2 — — Example 7-9 solution No. 3-9 Comparative Comparativeelectrolytic 130.6 127.9 123.5 — 37.7 — Example 7-10 solution No. 3-10Comparative Comparative electrolytic 134.1 130.3 123.8 — — Non- Example7-11 solution No. 3-11 combustible

Example 8—Negative Electrode: SiO_(x) Negative Electrode

With regard to Example 8, a powder mixture of a silicon oxide powder andan aggregated artificial graphite powder was used as anegative-electrode active material in place of the negative-electrodeactive material (a powder mixture of an artificial graphite and naturalgraphite) used in the nonaqueous electrolytic solution batteriesaccording to Example 7.

<Production of SiO_(x) Negative Electrode>

A powder mixture of a silicon oxide powder disproportioned by heattreatment (SiO_(x) wherein x is 0.3 to 1.6, the mean particle size: 5μm, Sigma Aldrich Japan, Co. LLC.) as a silicon oxide powder and MAG-D(the particle size: 20 μm or less) from Hitachi Chemical Co., Ltd. as anaggregated artificial graphite powder was uniformly dispersed and mixedinto NMP in which PVDF as a binding agent was pre-dissolved, and Ketjenblack (electrically conductive agent) was further added and mixed, andNMP for adjusting the viscosity was then further added to prepare anSiO_(x) mixture paste.

The above paste was applied to a copper foil (current collector), dried,and pressurized. Then the copper foil was processed into a predeterminedsize to obtain a test SiO_(x) negative electrode. The ratio of solidcontents in the negative electrode was SiO_(x):MAG-D:electricallyconductive agent:PVDF=35:47:8:10 (by the mass ratio).

It is noted that the amounts of the NMC positive-electrode activematerial and the SiO_(x) powder were adjusted so that the chargingcapacity of the SiO_(x) negative electrode is larger than that of theNMC positive electrode, and the applied amount was also adjusted so thata lithium metal does not deposit on the SiO_(x) negative electrodeduring charging.

(Preparation of Nonaqueous Electrolytic Solutions)

The nonaqueous electrolytic solutions Nos. 4-1 to 4-3 according to thepresent invention and the comparative electrolytic solutions Nos. 4-1 to4-5 were prepared in a similar way as in the nonaqueous electrolyticsolution No. 1-1 and the comparative electrolytic solutions Nos. 13-1 to13-8 except that FEC was added as a nonaqueous solvent.

That is, LiPF₆ as an electrolyte was dissolved and prepared in EC, EMC,and FEC (volume ratio 15:70:15/mass ratio 17.5:62.6:19.9) as anonaqueous solvent so that the concentration of LiPF₆ was 1.2 mol/L, andthen various ionic complex/EMC solutions according to the presentinvention and the group (II) compounds above were added to prepare thenonaqueous electrolytic solutions Nos. 4-1 to 4-3 and comparativeelectrolytic solutions Nos. 4-1 to 4-5 shown in Table 12 below.

TABLE 12 Group (II) Li salt Nonaqueous solvent compound LiPF₆ EC EMC FECCis Content Group (II) Electrolytic solution No, (mol/liter) (mass %)(mass %) (mass %) isomer (mass %) compound Electrolytic solution 1.217.5 62.6 19.9 (1a-Cis) 1.2 (II-1-5) No. 4-1 Electrolytic solution(II-3-14) No. 4-2 Electrolytic solution (II-5-1) No. 4-3 Comparativeelectrolytic — — — solution No. 4-1 1.2 17.5 62.6 19.9 — Comparativeelectrolytic (1a-Cis) 1.2 solution No. 4-2 Comparative electrolytic — —(II-1-5) solution No. 4-3 Comparative electrolytic — — (II-3-14)solution No. 4-4 Comparative electrolytic — — (II-5-1) solution No. 4-5Tetra- Trans Group fluoro isomer/ (IV) complex/ Group (III) Cis compoundCis compound isomer Tetra- isomer Content Trans Content (mass fluoroContent (mass Electrolytic solution No, (mass %) isomer (mass %) ratio)complex (mass %) ratio) Electrolytic solution 3.6 (1a-Trans) 0.006 0.005(5a-Tetra) 0.144 0.12 No. 4-1 Electrolytic solution 1.8 No. 4-2Electrolytic solution 18 No. 4-3 Comparative electrolytic — — — — — — —solution No. 4-1 Comparative electrolytic — — — — — — — solution No. 4-2Comparative electrolytic 3.6 (1a-Trans) 1.2 — (5a-Tetra) 0.144 —solution No. 4-3 Comparative electrolytic 1.8 solution No. 4-4Comparative electrolytic 18 solution No. 4-5<Production of Nonaqueous Electrolytic Solution Batteries>

Aluminum laminate housing cells (with a capacity of 30 mAh) includingthe above test NMC positive electrode, the test SiO_(x) negativeelectrode, and a microporous polypropylene-polyethylene double layeredseparator were respectively impregnated with one of the variousnonaqueous electrolytic solutions and the various comparative nonaqueouselectrolytic solutions shown in Table 12 to produce the nonaqueouselectrolytic solution batteries according to Examples 8-1 to 8-3 andComparative Examples 8-1 to 8-5 as in Example 7 and Comparative Example7 described above.

<Evaluation of Nonaqueous Electrolytic Solution Batteries>

<Evaluation 1> Low-Temperature Property (0° C.) after 200 Cycles at 60°C.

Each of the nonaqueous electrolytic solution batteries according toExample 8 and Comparative Example 8 was subjected to the followingevaluation.

First, constant-current and constant-voltage charge was performed as theinitial charge/discharge at an environmental temperature of 25° C. usingthe produced cells to a charge upper limit voltage of 4.2 V at a 0.05 Crate (1.5 mA), and discharge was performed at a constant current of a0.1 C rate (3 mA) to a discharge cutoff voltage of 2.5 V. Subsequently,the following charge-discharge cycle was repeated for 5 times to performconditioning: constant-current and constant-voltage charge was performedat a 0.1 C rate (3 mA) to a charge upper limit voltage of 4.2 V, anddischarge was performed at a constant current of a 0.1 C rate (3 mA) toa discharge cutoff voltage of 2.5 V.

After this conditioning, the following charge-discharge cycle wasrepeated for 3 times at an environmental temperature of 25° C.:constant-current and constant-voltage charge was performed at 0.2 C rate(6 mA) to a charge upper limit voltage of 4.2 V, and discharge was thenperformed at a constant current of a 0.2 C rate (6 mA) to a dischargecutoff voltage of 2.5 V.

Then, charge/discharge tests were performed at an environmentaltemperature of 60° C. The following charge-discharge cycle was repeatedfor 200 times: constant-current and constant-voltage charge wasperformed at a 1 C rate (30 mA) to a charge upper limit voltage of 4.2V, and discharge was performed at a constant current of a 2 C rate (60mA) to a discharge cutoff voltage of 2.5 V.

Next, the nonaqueous electrolytic solution batteries were cooled to 25°C., and again discharged to 2.5 V. Then constant-current andconstant-voltage charge was performed to 4.2 V at a 0.2 C rate at 0° C.Further, discharge was performed at a constant current of a 3 C rate (90mA) to a discharge cutoff voltage of 2.5 V, and the capacity obtained atthat time was taken as the low-temperature property (0° C.) afterprolonged cycles at 60° C.

<Evaluation 2>3C-Rate Characteristic after 200 Cycles at 60° C.

After performing 200 cycles at an environmental temperature of 60° C. inEvaluation 1 as described above, the nonaqueous electrolytic solutionbatteries were cooled to 25° C., and then again discharged to 2.5 V.Subsequently, constant-current and constant-voltage charge was performedto 4.2 V at a 0.1 C rate at 25° C. Further, discharge was performed at aconstant current of a 3 C rate (90 mA) to a discharge cutoff voltage of2.5 V, and the capacity obtained at that time was taken as the 3C-ratecharacteristic (25° C.) after prolonged cycles at 60° C.

<Evaluation 3> Low-Temperature Property (0° C.) after Stored at 60° C.

Each of the nonaqueous electrolytic solution batteries according toExample 8 and Comparative Example 8 was subjected to storage tests(stored for 10 days after changed to 4.2 V) at an environmentaltemperature of 60° C.

Next, the nonaqueous electrolytic solution batteries were cooled to 25°C., and again discharged to 2.5 V. Then constant-current andconstant-voltage charge was performed to 4.2 V at a 0.2 C rate at 0° C.Further, discharge was performed at a constant current of a 3 C rate(900 mA) to a discharge cutoff voltage of 2.5 V while maintaining thetemperature at 0° C., and the capacity obtained at that time was takenas the low-temperature property (0° C.) after stored at 60° C.

Evaluations 1 to 3 of the nonaqueous electrolytic solution batteriesaccording to Example 8 and Comparative Example 8 are shown in Table 13as relative values when Evaluations 1 to 3 of the nonaqueouselectrolytic solution battery according to Comparative Example 8-1 aretaken as 100.

<Evaluation 4> Evaluation of Expansion During Charge

Evaluations were performed as in Example 1-1 except that charge to 4.3 Vwas changed to charge to 4.2 V.

<Evaluation 5> Temperature Rise Value During Overcharging Test, and

<Evaluation 6> Evaluation of Combustibility

Evaluations were performed as in Example 1-1.

TABLE 13 (Positive electrode; NMC Negative electrode; SiO_(x) negativeelectrode) Low-temperature 3C-rate Low-temperature propertycharacteristic property (0° C.) (25° C.) (0° C.) Expansion Temperatureafter prolonged after prolonged after stored rate rise valueCombustibility Electrolytic solution No, cycles at 60° C. cycles at 60°C. at 60° C. (%) (K) test Example 8-1 Electrolytic solution No. 4-1133.2 135.4 117.5 6.7 — — Example 8-2 Electrolytic solution No. 4-2129.7 131.5 117.6 — 42.7 — Example 8-3 Electrolytic solution No. 4-3131.9 136.4 118.8 — — Non- combustible Comparative Comparativeelectrolytic 100.0 100.0 100.0 13.3 >99.9 Combustible Example 8-1solution No. 4-1 Comparative Comparative electrolytic 127.7 132.6 113.311.7 >99.9 Combustible Example 8-2 solution No. 4-2 ComparativeComparative electrolytic 128.6 132.5 114.3 8.3 — — Example 8-3 solutionNo. 4-3 Comparative Comparative electrolytic 124.1 128.8 113.0 — 46.7 —Example 8-4 solution No. 4-4 Comparative Comparative electrolytic 127.6132.4 114.1 — — Non- Example 8-5 solution No. 4-5 combustible

Example 9—Negative Electrode: Si Negative Electrode

With regard to Example 9, an Si powder was used as a negative-electrodeactive material in place of the negative-electrode active material (apowder mixture of a silicon oxide powder and an aggregated artificialgraphite powder) used in the nonaqueous electrolytic solution batteriesaccording to Example 8.

<Production of Test Si Negative Electrode>

An Si powder (a powder mixture with the mean particle size: 10 μm/6μm=9/1 by the mass ratio) as an Si powder was uniformly dispersed andmixed into NMP in which PVDF as a binding agent was pre-dissolved, andKetjen black (electrically conductive agent 1) and vapor-grown carbonfiber (VGCF®-H, Showa Denko K. K.) (electrically conductive agent 2)were further added and mixed, and NMP for adjusting the viscosity wasthen further added to prepare an Si mixture paste.

The above paste was applied to a copper foil (current collector), dried,and pressurized.

Then the copper foil was processed into a predetermined size to obtain atest Si negative electrode.

The ratio of solid contents in the negative electrode was Sipowder:electrically conductive agent 1:electrically conductive agent2:PVDF=78:7:3:12 (by the mass ratio).

It is noted that the amounts of the NMC positive-electrode activematerial and the Si powder were adjusted so that the charging capacityof the Si negative electrode is larger than that of the NMC positiveelectrode, and the applied amount was adjusted so that a lithium metaldoes not deposit on the Si negative electrode during charging.

<Production of Nonaqueous Electrolytic Solution Batteries>

Aluminum laminate housing cells (with a capacity of 30 mAh) includingthe above test NMC positive electrode, the test Si negative electrode,and a microporous polypropylene-polyethylene double layered separatorwere respectively impregnated with one of the various nonaqueouselectrolytic solutions and the various comparative nonaqueouselectrolytic solutions shown in Table 12 to produce the nonaqueouselectrolytic solution batteries according to Example 9 and ComparativeExample 9 as in Example 8 described above.

Example 9 and Comparative Example 9: Evaluation of NonaqueousElectrolytic Solution Batteries

The evaluations described above were performed as the following as inthe nonaqueous electrolytic solution batteries according to Example 8described above.

<Evaluation 1> Low-temperature property (0° C.) after 200 cycles at 60°C.

<Evaluation 2>3C-rate characteristic after 200 cycles at 60° C.

<Evaluation 3> Low-temperature property (0° C.) after stored at 60° C.

<Evaluation 4> Evaluation of expansion during charge

<Evaluation 5> Temperature rise value during overcharging test

<Evaluation 6> Evaluation of combustibility

Evaluations 1 to 3 of the nonaqueous electrolytic solution batteriesaccording to Example 9 and Comparative Example 9 are shown in Table 14as relative values when the results in Evaluations 1 to 3 of thenonaqueous electrolytic solution battery according to ComparativeExample 9-1 are taken as 100.

TABLE 14 (Positive electrode; NMC Negative electrode; Si negativeelectrode) Low-temperature 3C-rate Low-temperature propertycharacteristic property (0° C.) (25° C.) (0° C.) Expansion Temperatureafter prolonged after prolonged after stored rate rise valueCombustibility Electrolytic solution No, cycles at 60° C. cycles at 60°C. at 60° C. (%) (K) test Example 9-1 Electrolytic solution No. 4-1128.4 132.2 113.6 8.3 — — Example 9-2 Electrolytic solution No. 4-2124.1 128.0 112.9 — 44.4 — Example 9-3 Electrolytic solution No. 4-3134.7 132.3 114.3 — — Non- combustible Comparative Comparativeelectrolytic 100.0 100.0 100.0 15.0 >99.9 Combustible Example 9-1solution No. 4-1 Comparative Comparative electrolytic 124.4 128.7 110.812.5 >99.9 Combustible Example 9-2 solution No. 4-2 ComparativeComparative electrolytic 125.0 129.4 110.5 10.0 — — Example 9-3 solutionNo. 4-3 Comparative Comparative electrolytic 121.5 125.8 109.9 — 50.0 —Example 9-4 solution No. 4-4 Comparative Comparative electrolytic 124.5128.9 111.2 — — Non- Example 9-5 solution No. 4-5 combustible

Example 10 and Comparative Example 10—Negative Electrode: LTO NegativeElectrode

In Example 10, a Li₄Ti₅O₁₂ (LTO) powder was used as a negative-electrodeactive material in place of the negative-electrode active material (anSi powder) used in Example 9.

<Production of Test LTO Negative Electrode>

An LTO powder (a powder mixture with the mean particle size: 0.90μm/3.40 μm=9/1 by the mass ratio) as an Li₄Ti₅O₁₂ (LTO) powder wasuniformly dispersed and mixed into NMP in which PVDF as a binding agentwas pre-dissolved, and Ketjen black (electrically conductive agent 1)and vapor-grown carbon fiber (VGCF®-H, Showa Denko K. K.) (electricallyconductive agent 2) were further added and mixed, and NMP for adjustingthe viscosity was then further added to prepare an LTO mixture paste.

The resulting paste was applied to an aluminum foil (current collector),dried, and pressurized. Then the aluminum foil was processed into apredetermined size to obtain a test LTO negative electrode.

The ratio of solid contents in the negative electrode was LTOpowder:electrically conductive agent 1:electrically conductive agent2:PVDF=83:5:2:10 (by the mass ratio).

(Preparation of Nonaqueous Electrolytic Solutions)

[Preparation of Nonaqueous Electrolytic Solutions Nos. 5-1 to 5-6 andComparative Electrolytic Solutions Nos. 5-1 to 5-5]

In a dry box under a nitrogen atmosphere of a dew point of −50° C. orless, LiPF₆ and LiBF₄ as electrolytes were dissolved and prepared in anonaqueous solvent of PC and EMC (volume ratio 30:70/mass ratio33.8:66.2) so that the concentrations of LiPF₆ and LiBF₄ were 1.1mol/liter and 0.4 mol/liter, respectively, and then various ioniccomplex/EMC solutions according to the present invention and the group(II) compounds as described above were added to prepare the nonaqueouselectrolytic solutions Nos. 5-1 to 5-6 and the comparative electrolyticsolutions Nos. 5-1 to 5-5 shown in Table 15.

TABLE 15 Group Group (I) (III) LiPF₆ LiBF₄ compound Content GroupContent compound (mol/ (mol/ (Cis (mass (II) (mass Trans Electrolyticsolution No, liter) liter) isomer) %) compound %) isomer Electrolyticsolution No. 5-1 1.1 0.4 (1a-Cis) 1.2 (II-1-5) 3.6 — Electrolyticsolution No. 5-2 (1a-Trans) Electrolytic solution No. 5-3 (1a-Cis) 1.2(II-3-14) 1.8 — Electrolytic solution No. 5-4 (1a-Trans) Electrolyticsolution No. 5-5 (1a-Cis) 1.2 (II-5-1) 18.0 — Electrolytic solution No.5-6 (1a-Trans) Comparative electrolytic 1.1 0.4 — — — — — solution No.5-1 Comparative electrolytic (1a-Cis) 1.2 — — — solution No. 5-2Comparative electrolytic — — (II-1-5) 3.6 (1a-Trans) solution No. 5-3Comparative electrolytic — — (II-3-14) 1.8 (1a-Trans) solution No. 5-4Comparative electrolytic — — (II-5-1) 18.0 (1a-Trans) solution No. 5-5Tetra- Trans Group fluoro isomer/ (IV) complex/ Cis compound Cis Contentisomer Tetra- Content isomer (mass (mass fluoro (mass (mass Electrolyticsolution No, %) ratio) complex %) ratio) Electrolytic solution No. 5-1 —— — — — Electrolytic solution No. 5-2 0.006 0.005 (5a-Tetra) 0.144 0.12Electrolytic solution No. 5-3 — — — — — Electrolytic solution No. 5-40.006 0.005 (5a-Tetra) 0.144 0.12 Electrolytic solution No. 5-5 — — — —— Electrolytic solution No. 5-6 0.006 0.005 (5a-Tetra) 0.144 0.12Comparative electrolytic — — — — — solution No. 5-1 Comparativeelectrolytic — — — — — solution No. 5-2 Comparative electrolytic 1.2 —(5a-Tetra) 0.144 — solution No. 5-3 Comparative electrolytic 1.2 —(5a-Tetra) 0.144 — solution No. 5-4 Comparative electrolytic 1.2 —(5a-Tetra) 0.144 — solution No. 5-5<Production of Nonaqueous Electrolytic Solution Batteries>

Aluminum laminate housing cell (with a capacity of 30 mAh) including theabove test NMC positive electrode, the test LTO negative electrode, anda cellulose separator were respectively impregnated with one of thevarious nonaqueous electrolytic solutions and the various comparativenonaqueous electrolytic solutions shown in Table 15 to produce thenonaqueous electrolytic solution batteries according to Examples 10-1 to10-6 and Comparative Examples 10-1 to 10-5 as in Example 9 describedabove.

<Evaluation of Nonaqueous Electrolytic Solution Batteries>

<Evaluation 1> Low-Temperature Property (0° C.) after 500 Cycles at 60°C.

Each of the nonaqueous electrolytic solution batteries according toExample 10 and Comparative Example 10 was subjected to the followingevaluation.

First, conditioning was performed at an environmental temperature of 25°C. under the following conditions.

That is, constant-current and constant-voltage charge was performed asthe initial charge/discharge at an environmental temperature of 25° C.using the produced cells to a charge upper limit voltage of 2.8 V at a0.1 C rate (3 mA), and discharge was performed at a constant current ofa 0.1 C rate (3 mA) to a discharge cutoff voltage of 1.5 V.Subsequently, the following charge-discharge cycle was repeated for 3times: constant-current and constant-voltage charge was performed to acharge upper limit voltage of 2.8 V at a 0.1 C rate (3 mA), anddischarge was performed at a constant current of a 0.1 C rate (3 mA) toa discharge cutoff voltage of 1.5 V.

After this conditioning, the following charge-discharge cycle wasrepeated for 3 times at an environmental temperature of 25° C.:constant-current and constant-voltage charge was performed at 0.2 C rate(6 mA) to a charge upper limit voltage of 2.8 V, and discharge was thenperformed at a constant current of a 0.2 C rate (6 mA) to a dischargecutoff voltage of 1.5 V.

Then, charge/discharge tests were performed at an environmentaltemperature of 60° C. The following charge-discharge cycle was repeatedfor 500 times: constant-current and constant-voltage charge wasperformed at a 2 C rate (30 mA) to a charge upper limit voltage of 2.8V, and discharge was performed at a constant current of a 2 C rate (60mA) to a discharge cutoff voltage of 1.5 V.

Next, the nonaqueous electrolytic solution batteries were cooled to 25°C., and again discharged to 1.5 V. Then constant-current andconstant-voltage charge was performed to 2.8 V at a 0.2 C rate at 0° C.Further, discharge was performed at a constant current of a 5 C rate(150 mA) to a discharge cutoff voltage of 1.5 V, and the capacityobtained at that time was taken as the low-temperature property (0° C.)after prolonged cycles at 60° C.

<Evaluation 2>5C-Rate Characteristic after 500 Cycles at 60° C.

After performing 500 cycles at an environmental temperature of 60° C. inEvaluation 1 as described above, the nonaqueous electrolytic solutionbatteries were cooled to 25° C., and then again discharged to 1.5 V.Subsequently constant-current and constant-voltage charge was performedto 2.8 V at a 0.1 C rate at 25° C. Further, discharge was performed at aconstant current of a 5 C rate (150 mA) to a discharge cutoff voltage of1.5 V while maintaining the temperature at 25° C., and the capacityobtained at that time was taken as the 5C-rate characteristic (25° C.)after prolonged cycles at 60° C.

<Evaluation 3> Low-Temperature Property (0° C.) after Stored at 60° C.

Each of the nonaqueous electrolytic solution batteries according toExample 10 and Comparative Example 10 was subjected to storage tests(stored for 10 days after charged to 2.8 V) at an environmentaltemperature of 60° C.

Next, the nonaqueous electrolytic solution batteries were cooled to 25°C., and again discharged to 1.5 V. Then constant-current andconstant-voltage charge was performed to 2.8 V at a 0.2 C rate at 0° C.Further, discharge was performed at a constant current of a 5 C rate(150 mA) to a discharge cutoff voltage of 1.5 V while maintaining thetemperature at 0° C., and the capacity obtained at that time was takenas the low-temperature property (0° C.) after stored at 60° C.

Evaluations 1 to 3 of the nonaqueous electrolytic solution batteriesaccording to Example 10 and Comparative Example 10 are shown in Table 16as relative values when Evaluations 1 to 3 of the nonaqueouselectrolytic solution battery according to Comparative Example 10-1 aretaken as 100.

<Evaluation 4> Evaluation of Expansion During Charge

Evaluations were performed as in Example 1-1 except that charge to 4.3 Vwas changed to charge to 2.8 V.

<Evaluation 5> Temperature Rise Value During Overcharging Test, and

<Evaluation 6> Evaluation of Combustibility

Evaluations were performed as in Example 1-1.

TABLE 16 (Positive electrode; NMC Negative electrode; LTO negativeelectrode) Low-temperature 5C-rate Low-temperature propertycharacteristic property (0° C.) (25° C.) (0° C.) Expansion Temperatureafter prolonged after prolonged after stored rate rise valueCombustibility Electrolytic solution No, cycles at 60° C. cycles at 60°C. at 60° C. (%) (K) test Example 10-1 Electrolytic solution No. 5-1121.4 126.9 110.1 4.2 — — Example 10-2 Electrolytic solution No. 5-2121.9 127.2 110.4 — 30.6 — Example 10-3 Electrolytic solution No. 5-3116.0 119.6 110.6 — — Non- combustible Example 10-4 Electrolyticsolution No. 5-4 116.4 120.1 111.4 3.3 — — Example 10-5 Electrolyticsolution No. 5-5 120.2 125.6 110.3 — 29.6 — Example 10-6 Electrolyticsolution No. 5-6 121.0 125.6 110.5 — — Non- combustible ComparativeComparative electrolytic 100.0 100.0 100.0 11.7 83.4 Combustible Example10-1 solution No. 5-1 Comparative Comparative electrolytic 119.6 126.1108.8 10.0 83.4 Combustible Example 10-2 solution No. 5-2 ComparativeComparative electrolytic 120.3 126.5 109.1 6.7 — — Example 10-3 solutionNo. 5-3 Comparative Comparative electrolytic 114.4 118.3 108.0 — 33.0 —Example 10-4 solution No. 5-4 Comparative Comparative electrolytic 118.5124.8 108.6 — — Non- Example 10-5 solution No. 5-5 combustible(Regarding Examples 6 to 10)

Examples 6-1 to 6-6, Examples 7-1 to 7-6, Examples 8-1 to 8-3, Examples9-1 to 9-3, and Examples 10-1 to 10-6 were found to improve all ofEvaluations 1 to 3 as compared with Comparative Examples not includingthese (Comparative Example 6-1, Comparative Example 7-1, ComparativeExample 8-1, Comparative Example 9-1, and Comparative Example 10-1), byusing the nonaqueous electrolytic solution that uses a combination of(1a-Cis) from Synthesis Example 1 as the group (I) compound according toExample and the group (II) compound and that may include the group (III)compound and the group (IV) compound, even in a case where an amorphouscarbon powder (Carbotron® P), a powder mixture of an artificial graphiteand natural graphite, a powder mixture of a silicon oxide powder and anaggregated artificial graphite powder, an Si powder, or LTO is usedinstead of a graphite powder as a negative-electrode active material.

Further, the nonaqueous electrolytic solution batteries including thedifluoro ionic complex (1a-Cis) in the cis configuration and the group(II) compound were found to be excellent in Evaluations 1 to 3 ascompared with the nonaqueous electrolytic solution batteries includingthe difluoro ionic complex (1a-Trans) in the trans configuration and thegroup (II) compound.

Further, Examples including the cyclic phosphazene compound (II-1-5)were able to prevent expansion of the cells during charge as comparedwith Comparative Examples not including this.

Further, Examples including the aromatic compound (II-3-14) were able toprevent temperature rise during overcharging as compared withComparative Examples not including this.

Further, Examples including the phosphoric acid ester compound (II-5-1)showed non-combustibility in the combustibility test and were able tomake the electrolytic solution more flame-retardant as compared withComparative Examples not including this.

As described above, it is found that the nonaqueous electrolyticsolutions according to the present invention can show similar effects asExample 1 in any of the cases where the following materials were used asa negative electrode: a carbon material having a d value in the latticeplane (002) of more than 0.340 nm as determined by X ray diffraction; acarbon material having a d value in the lattice plane (002) of 0.340 nmor less as determined by X ray diffraction; an oxide of one or moremetals selected from Si, Sn, and Al; one or more metals selected fromSi, Sn, and Al, and an alloy comprising the one or more metals andfurther comprising or not comprising lithium; and a lithium titaniumoxide.

That is, it is clear that the nonaqueous electrolytic solution accordingto the present invention and a battery using this have effects ofimproving cycle characteristics regardless of the types of negativeelectrodes as in the case of the positive electrode described above.Further, the nonaqueous electrolytic solution according to the presentinvention and batteries using this are capable of exerting effects ofimproving safety of batteries such as flame retardancy, prevention ofexpansion during charge and discharge, or prevention of overcharging,depending on the combinedly used compound shown in group II.

The invention claimed is:
 1. A nonaqueous electrolytic solution fornonaqueous electrolytic solution secondary batteries, the nonaqueouselectrolytic solution comprising: a nonaqueous solvent, an electrolytedissolved in the nonaqueous solvent, (I) a difluoro ionic complex (1)represented by the general formula (1), and (II) at least one compoundselected from the group consisting of a cyclic phosphazene compoundrepresented by the general formula (II-1) below, a siloxane compoundrepresented by the general formula (II-2) below, an aromatic compoundrepresented by the general formula (II-3) below, a cyclohexene compoundrepresented by the general formula (II-4) below, a phosphoric acid estercompound represented by the general formula (II-5) below, a fluorinatedlinear ether compound represented by the general formula (II-6) below, afluorinated cyclic ether compound represented by the general formula(II-7) below, and a boric acid ester compound represented by the generalformula (II-8) below, wherein 95 mol % or more of the difluoro ioniccomplex (1) is a difluoro ionic complex (1-Cis) in a cis configurationrepresented by the general formula (1-Cis),

wherein in (1-Cis),

wherein in the general formula (1) and the general formula (1-Cis), A⁺is any one selected from the group consisting of a metal ion, a proton,and an onium ion, and M is any one selected from the group consisting ofSi, P, As, and Sb; F is a fluorine atom; O is an oxygen atom; t is 2when M is Si, and t is 1 when M is P, As, or Sb; X is an oxygen atom or—N(R¹)—; N is a nitrogen atom; and R¹ is a hydrocarbon group having 1 to10 carbon atoms and optionally having a hetero atom and/or a halogenatom (the hydrocarbon group optionally having a branched-chain or ringstructure when the number of carbon atoms is 3 or more); when X is—N(R¹)—, and p is 0, X and W are bonded directly and optionally form astructure as shown in at least one selected from the general formulas(1-Cis-1) to (1-Cis-3) below; in the case of the general formula(1-Cis-2) below where the direct bond is a double bond, R¹ is notpresent, Y is a carbon atom or a sulfur atom; q is 1 when Y is a carbonatom; q is 1 or 2 when Y is a sulfur atom; W represents a hydrocarbongroup having 1 to 10 carbon atoms and optionally having a hetero atomand/or a halogen atom (the hydrocarbon group optionally having abranched-chain or ring structure when the number of carbon atoms is 3 ormore), or —N(R²)—; wherein, R² represents a hydrogen atom, an alkalinemetal, or a hydrocarbon group having 1 to 10 carbon atoms and optionallyhaving a hetero atom and/or a halogen atom; when the number of carbonatoms is 3 or more, R² optionally has a branched-chain or ringstructure; p is 0 or 1, q is an integer of 0 to 2, r is an integer of 0to 2, and further, p+r≥1,

wherein in the general formula (II-1), R¹ to R⁶ are each independently asubstituent selected from the group consisting of a halogen atom, anamino group, an alkyl group having 1 to 10 carbon atoms, an alkoxy grouphaving 1 to 10 carbon atoms, and an aryloxy group having 6 to 12 carbonatoms; n¹ is an integer of 1 to 10; and the alkyl group, the alkoxygroup, and the aryloxy group optionally have a hetero atom and/or ahalogen atom; in the general formula (II-2), R⁷ to R¹² are eachindependently a substituent selected from the group consisting of analkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10carbon atoms, an alkenyl group having 2 to 10 carbon atoms, analkenyloxy group having 2 to 10 carbon atoms, an alkynyl group having 2to 10 carbon atoms, an alkynyloxy group having 2 to 10 carbon atoms, anaryl group having 6 to 12 carbon atoms, and an aryloxy group having 6 to12 carbon atoms, said groups optionally having a hetero atom and/or ahalogen atom; n² is an integer of 1 to 10; when n² is 2 or more, R¹¹'sand R¹²'s independently are optionally the same as or different from oneanother; a group represented by OR⁷ and a group represented by OR⁸ areoptionally bonded to each other to form a siloxane bond; and thesiloxane compound represented by the general formula (II-2) includes asiloxane compound represented by the general formula (II-2′); and in thegeneral formula (11-2′), R¹³ and R¹⁴ are each independently asubstituent selected from the group consisting of an alkyl group having1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, analkenyl group having 2 to 10 carbon atoms, an alkenyloxy group having 2to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, analkynyloxy group having 2 to 10 carbon atoms, an aryl group having 6 to12 carbon atoms, and an aryloxy group having 6 to 12 carbon atoms, saidgroups optionally having a hetero atom and/or a halogen atom; n³ is aninteger of 2 to 10; R¹³'s and R¹⁴'s independently are optionally thesame as or different from one another;

wherein in the general formula (II-3), R¹⁵ to R²⁰ are each independentlya substituent selected from the group consisting of a hydrogen atom, ahalogen atom, and a hydrocarbon group having 1 to 12 carbon atoms; andat least two of R¹⁵ to R²⁰ are optionally bonded to one another to forma ring; and in the general formula (II-4), R²¹ to R²⁴ are eachindependently a substituent selected from the group consisting of ahydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 12carbon atoms; and at least two of R²¹ to R²⁴ are optionally bonded toone another to form a ring;

wherein in the general formula (II-5), R²⁵ to R²⁷ are each independentlya substituent selected from the group consisting of an alkyl grouphaving 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms,an alkenyl group having 2 to 10 carbon atoms, a cyano group, an aminogroup, a nitro group, an alkoxy group having 1 to 10 carbon atoms, and acycloalkyl group having 3 to 10 carbon atoms, said groups optionallyhaving a hetero atom and/or a halogen atom; and any two or all of R²⁵,R²⁶, and R²⁷ are optionally bonded to one another to form a ringstructure; in the general formula (II-6), R²⁸ and R²⁹ are eachindependently a substituent selected from the group consisting of analkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to10 carbon atoms, a fluorinated alkyl group having 1 to 10 carbon atoms,a fluorinated cycloalkyl group having 3 to 10 carbon atoms, an alkylgroup having 1 to 10 carbon atoms and having an ethereal oxygen atombetween the carbon atoms, and a fluorinated alkyl group having 1 to 10carbon atoms and having an ethereal oxygen atom between the carbonatoms; and at least one of R²⁸ and R²⁹ contains a fluorine atom; in thegeneral formula (II-7), R³² is a substituent selected from the groupconsisting of an alkylene group having 1 to 5 carbon atoms, afluorinated alkylene group having 1 to 5 carbon atoms, an alkylene grouphaving 1 to 5 carbon atoms and having an ethereal oxygen atom betweenthe carbon atoms, and a fluorinated alkylene group having 1 to 5 carbonatoms and having an ethereal oxygen atom between the carbon atoms; R³⁰and R³¹ are each independently a substituent selected from the groupconsisting of an alkyl group having 1 to 10 carbon atoms, a cycloalkylgroup having 3 to 10 carbon atoms, a fluorinated alkyl group having 1 to10 carbon atoms, a fluorinated cycloalkyl group having 3 to 10 carbonatoms, an alkyl group having 1 to 10 carbon atoms and having an etherealoxygen atom between the carbon atoms, and a fluorinated alkyl grouphaving 1 to 10 carbon atoms and having an ethereal oxygen atom betweenthe carbon atoms; and at least one of R³⁰ and R³¹ contains a fluorineatom; and in the general formula (II-8), R³³ to R³⁵ are eachindependently a fluorinated alkyl group having 1 to 10 carbon atoms. 2.The nonaqueous electrolytic solution according to claim 1, wherein acombination of M, X, Y, W, p, q, r, and tin an anion moiety of thedifluoro ionic complex (1) and in an anion moiety of the difluoro ioniccomplex (1-Cis) is at least one combination selected from (Cis-a),(Cis-b), (Cis-c), and (Cis-d): (Cis-a) M=P; X=O; Y=C; p=q=t=1; and r=0;(Cis-b) M=P; X=O; W=C(CF₃)₂; p=q=0; and r=t=1; (Cis-c) M=Si; X=O; Y=C;p=q=1; t=2; and r=0; and (Cis-d) M=P; X=N(R¹); Y=C; R¹=CH₃; p=q=t=1; andr=0.
 3. The nonaqueous electrolytic solution according to claim 1,wherein the A⁺ in the difluoro ionic complex (1-Cis) comprises at leastone selected from the group consisting of a lithium ion, a sodium ion, apotassium ion, and a quaternary alkylammonium ion.
 4. The nonaqueouselectrolytic solution according to claim 1, wherein the content of thedifluoro ionic complex (1-Cis) is in the range of 0.001 mass % or moreand 20 mass % or less relative to the nonaqueous electrolytic solution.5. The nonaqueous electrolytic solution according to claim 1, whereinthe content of the compound shown in the (II) above is in the range of0.01 mass % or more and 50 mass % or less relative to the nonaqueouselectrolytic solution, in the case where the compound shown in the (II)above comprises a cyclic phosphazene compound represented by the generalformula (II-1) above, the content of the cyclic phosphazene compoundrepresented by the general formula (II-1) above is in the range of 0.5mass % or more and 15 mass % or less relative to the nonaqueouselectrolytic solution, in the case where the compound shown in the (II)above comprises a siloxane compound represented by the general formula(II-2) above, the content of the siloxane compound represented by thegeneral formula (II-2) above is in the range of 0.01 mass % or more and10 mass % or less relative to the nonaqueous electrolytic solution, inthe case where the compound shown in the (II) above comprises anaromatic compound represented by the general formula (II-3) above, thecontent of the aromatic compound represented by the general formula(II-3) above is in the range of 0.01 mass % or more and 10 mass % orless relative to the nonaqueous electrolytic solution, in the case wherethe compound shown in the (II) above comprises a cyclohexene compoundrepresented by the general formula (II-4) above, the content of thecyclohexene compound represented by the general formula (II-4) above isin the range of 0.01 mass % or more and 10 mass % or less relative tothe nonaqueous electrolytic solution, in the case where the compoundshown in the (II) above comprises a phosphoric acid ester compoundrepresented by the general formula (II-5) above, the content of thephosphoric acid ester compound represented by the general formula (II-5)above is in the range of 5 mass % or more and 40 mass % or less relativeto the nonaqueous electrolytic solution, in the case where the compoundshown in the (II) above comprises a fluorinated linear ether compoundrepresented by the general formula (II-6) above, the content of thephosphoric acid ester compound represented by the general formula (II-6)above is in the range of 10 mass % or more and 50 mass % or lessrelative to the nonaqueous electrolytic solution, in the case where thecompound shown in the (II) above comprises a fluorinated cyclic ethercompound represented by the general formula (II-7) above, the content ofthe fluorinated cyclic ether compound represented by the general formula(II-7) above is in the range of 10 mass % or more and 50 mass % or lessrelative to the nonaqueous electrolytic solution, and in the case wherethe compound shown in the (II) above comprises a boric acid estercompound represented by the general formula (II-8) above, the content ofthe boric acid ester compound represented by the general formula (II-8)above is in the range of 3 mass % or more and 30 mass % or less relativeto the nonaqueous electrolytic solution.
 6. The nonaqueous electrolyticsolution according to claim 1, wherein the difluoro ionic complex (1)further comprises (III) a difluoro ionic complex (1-Trans) in a transconfiguration represented by the general formula (1-Trans),

wherein in (1-Trans)

wherein in the general formula (1-Trans), A⁺ is any one selected fromthe group consisting of a metal ion, a proton, and an onium ion, and Mis any one selected from the group consisting of Si, P, As, and Sb; F isa fluorine atom; O is an oxygen atom; t is 2 when M is Si, and t is 1when M is P, As, or Sb; X is an oxygen atom or —N(R¹)—; N is a nitrogenatom; and R¹ is a hydrocarbon group having 1 to 10 carbon atoms andoptionally having a hetero atom and/or a halogen atom (the hydrocarbongroup optionally having a branched-chain or ring structure when thenumber of carbon atoms is 3 or more); when X is —N(R¹)—, and p is 0, Xand W are bonded directly and optionally form at least one structureselected from the general formulas (1-Trans-1) to (1-Trans-3) below; inthe case of the general formula (1-Trans-2) below where the direct bondis a double bond, R¹ is not present, Y is a carbon atom or a sulfuratom; q is 1 when Y is a carbon atom; q is 1 or 2 when Y is a sulfurato; W represents a hydrocarbon group having 1 to 10 carbon atoms andoptionally having a hetero atom and/or a halogen atom (the hydrocarbongroup optionally having a branched-chain or ring structure when thenumber of carbon atoms is 3 or more), or —N(R²)—; wherein R² representsa hydrogen atom, an alkaline metal, or a hydrocarbon group having 1 to10 carbon atoms and optionally having a hetero atom and/or a halogenatom; when the number of carbon atoms is 3 or more, R² optionally has abranched-chain or ring structure; p is 0 or 1, q is an integer of 0 to2, r is an integer of 0 to 2, and further, p+r≥1,


7. The nonaqueous electrolytic solution according to claim 6, wherein acombination of M, X, Y, W, p, q, r, and tin an anion moiety of thedifluoro ionic complex (1-Trans) is at least one combination selectedfrom (Trans-a), (Trans-b), (Trans-c), and (Trans-d) below: (Trans-a)M=P; X=O; Y=C; p=q=t=1; and r=0, (Trans-b) M=P; X=O; W=C(CF₃)₂; p=q=0;and r=t=1, (Trans-c) M=Si; X=O; Y=C; p=q=1; t=2; and r=0; and (Trans-d)M=P; X=N(R¹); Y=C; R¹=CH₃; p=q=t=1; and r=0.
 8. The nonaqueouselectrolytic solution according to claim 6, wherein the A⁺ in thedifluoro ionic complex (1-Trans) comprises at least one selected fromthe group consisting of a lithium ion, a sodium ion, a potassium ion,and a quaternary alkylammonium ion.
 9. The nonaqueous electrolyticsolution according to claim 6, wherein the mass ratio (1-Trans)/(1-Cis)of the difluoro ionic complex (1-Trans) to the difluoro ionic complex(1-Cis) is 0.0001 or more and 0.05 or less.
 10. The nonaqueouselectrolytic solution according to claim 1, further comprising (IV) atetrafluoro ionic complex represented by the general formula (1-Tetra):

wherein in the general formula (1-Tetra), A⁺ is any one selected fromthe group consisting of a metal ion, a proton, and an onium ion, and Mis any one selected from the group consisting of Si, P, As, and Sb; F isa fluorine atom; O is an oxygen atom; t is 2 when M is Si, and t is 1when M is P, As, or Sb; X is an oxygen atom or —N(R¹)—; N is a nitrogenatom; and R¹ is a hydrocarbon group having 1 to 10 carbon atoms andoptionally having a hetero atom and/or a halogen atom (the hydrocarbongroup optionally having a branched-chain or ring structure when thenumber of carbon atoms is 3 or more); when X is —N(R¹)—, and p is 0, Xand W are bonded directly and optionally form at least one structureselected from the general formulas (1-Tetra-1) to (1-Tetra-3) below; inthe case of the general formula (1-Tetra-2) below where the direct bondis a double bond, R¹ is not present, Y is a carbon atom or a sulfuratom, q is 1 when Y is a carbon atom, q is 1 or 2 when Y is a sulfuratom; W represents a hydrocarbon group having 1 to 10 carbon atoms andoptionally having a hetero atom and/or a halogen atom (the hydrocarbongroup optionally having a branched-chain or ring structure when thenumber of carbon atoms is 3 or more), or —N(R²)—; wherein R² representsa hydrogen atom, an alkaline metal, or a hydrocarbon group having 1 ormore and 10 or less carbon atoms and optionally having a hetero atomand/or a halogen atom; when the number of carbon atoms is 3 or more, R²optionally has a branched-chain or ring structure; p is 0 or 1, q is aninteger of 0 to 2, r is an integer of 0 to 2, and further, p+r≥1


11. The nonaqueous electrolytic solution according to claim 10, whereina combination of M, X, Y, W, p, q, r, and t in an anion moiety of thetetrafluoro ionic complex is at least one combination selected from(Tetra-a), (Tetra-b), (Tetra-c), and (Tetra-d): (Tetra-a) M=P; X=O; Y=C;p=q=t=1; and r=0, (Tetra-b) M=P; X=O; W=C(CF₃)₂; p=q=0; and r=t=1,(Tetra-c) M=Si; X=O; Y=C; p=q=1; t=2; and r=0; and (Tetra-d) M=P;X=N(R¹); Y=C; R¹=CH₃; p=q=t=1; and r=0.
 12. The nonaqueous electrolyticsolution according to claim 10, wherein the A⁺ in the tetrafluoro ioniccomplex (1-Tetra) comprises at least one selected from the groupconsisting of a lithium ion, a sodium ion, a potassium ion, and aquaternary alkylammonium ion.
 13. The nonaqueous electrolytic solutionaccording to claim 10, wherein the mass ratio (1-Tetra)/(1-Cis) of thetetrafluoro ionic complex (1-Tetra) to the difluoro ionic complex(1-Cis) is 0.02 or more and 0.25 or less.
 14. The nonaqueouselectrolytic solution according claim 1, wherein the nonaqueous solventcomprises at least one selected from the group consisting of a cycliccarbonate and a chain carbonate.
 15. The nonaqueous electrolyticsolution according to claim 14, wherein the cyclic carbonate comprisesat least one selected from the group consisting of ethylene carbonateand propylene carbonate, and the chain carbonate comprises at least oneselected from the group consisting of ethylmethyl carbonate, dimethylcarbonate, diethyl carbonate, and methylpropyl carbonate.
 16. Thenonaqueous electrolytic solution according to claim 14, wherein thenonaqueous solvent further comprises at least one selected from thegroup consisting of esters, ethers, lactones, nitriles, amides, andsulfones.
 17. The nonaqueous electrolytic solution according to claim14, wherein the nonaqueous solvent further comprises at least onecompound selected from the group consisting of vinylene carbonate,vinylethylene carbonate, ethynylethylene carbonate, and fluoroethylenecarbonate.
 18. The nonaqueous electrolytic solution according to claim1, wherein the electrolyte comprises a salt comprising a pair of acation and an anion, the cation being at least one selected from thegroup consisting of lithium, sodium, potassium, and quaternary ammonium,and the anion being at least one selected from the group consisting ofhexafluorophosphoric acid, tetrafluoroboric acid, perchloric acid,hexafluoroarsenic acid, hexafluoroantimonic acid,trifluoromethanesulfonic acid, bis(trifluoromethanesulfonyl)imide,bis(pentafluoroethanesulfonyl)imide,(trifluoromethanesulfonyl)(pentafluoroethanesulfonyl)imide,bis(fluorosulfonyl)imide,(trifluoromethanesulfonyl)(fluorosulfonyl)imide,(pentafluoroethanesulfonyl)(fluorosulfonyl)imide,tris(trifluoromethanesulfonyl)methide, and bis(difluorophosphonyl)imide.19. A nonaqueous electrolytic solution secondary battery comprising thenonaqueous electrolytic solution according to claim 1, a positiveelectrode, a negative electrode, and a separator.
 20. A nonaqueouselectrolytic solution secondary battery, comprising: (a) the nonaqueouselectrolytic solution according to claim 1; (b) a positive electrodeincluding at least one of oxide and a polyanion compound as apositive-electrode active material; (c) a negative electrode including anegative-electrode active material; and (d) a separator includingpolyolefin or cellulose as a main component, wherein thepositive-electrode active material is at least one selected from thegroup consisting of (A) a lithium-transition metal composite oxidecontaining at least one metal of nickel, manganese, and cobalt, andhaving a layered structure, (B) a lithium-manganese composite oxidehaving a spinel structure, (C) a lithium-containing olivine-typephosphate salt, and (D) a lithium-rich layered transition-metal oxidehaving a stratified rock-salt structure, and the negative-electrodeactive material is at least one selected from the group consisting of(E) a carbon material having a d value in a lattice plane (002) of 0.340nm or less as determined by X ray diffraction, (F) a carbon materialhaving a d value in the lattice plane (002) of more than 0.340 nm asdetermined by X ray diffraction, (G) an oxide of one or more metalsselected from Si, Sn, and Al, (H) one or more metals selected from Si,Sn, and Al, and an alloy comprising the one or more metals and furthercomprising or not comprising lithium, and (I) a lithium titanium oxide.